diff --git a/test/overlay/Kconfig b/test/overlay/Kconfig
new file mode 100644
index 0000000..13c8542
--- /dev/null
+++ b/test/overlay/Kconfig
@@ -0,0 +1,11 @@
+config UT_OVERLAY
+	bool "Enable Device Tree Overlays Unit Tests"
+	depends on OF_LIBFDT_OVERLAY
+	depends on UNIT_TEST
+	help
+	  This enables the 'ut overlay' command which runs a series of unit
+	  tests on the fdt overlay code.
+	  If all is well then all tests pass although there will be a few
+	  messages printed along the way.
+	  Be warned that it requires an out-of-tree dtc compiler with patches
+	  to support the DT overlays, otherwise it will fail.
diff --git a/test/overlay/Makefile b/test/overlay/Makefile
new file mode 100644
index 0000000..907f085
--- /dev/null
+++ b/test/overlay/Makefile
@@ -0,0 +1,15 @@
+#
+# Copyright (c) 2016 NextThing Co
+# Copyright (c) 2016 Free Electrons
+#
+# SPDX-License-Identifier:	GPL-2.0+
+#
+
+# Test files
+obj-y += cmd_ut_overlay.o
+
+DTC_FLAGS += -@
+
+# DT overlays
+obj-y += test-fdt-base.dtb.o
+obj-y += test-fdt-overlay.dtb.o
diff --git a/test/overlay/cmd_ut_overlay.c b/test/overlay/cmd_ut_overlay.c
new file mode 100644
index 0000000..87dc932
--- /dev/null
+++ b/test/overlay/cmd_ut_overlay.c
@@ -0,0 +1,268 @@
+/*
+ * Copyright (c) 2016 NextThing Co
+ * Copyright (c) 2016 Free Electrons
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <command.h>
+#include <errno.h>
+#include <malloc.h>
+
+#include <linux/sizes.h>
+
+#include <test/ut.h>
+#include <test/overlay.h>
+
+/* 4k ought to be enough for anybody */
+#define FDT_COPY_SIZE	(4 * SZ_1K)
+
+extern u32 __dtb_test_fdt_base_begin;
+extern u32 __dtb_test_fdt_overlay_begin;
+
+static int fdt_getprop_u32_by_index(void *fdt, const char *path,
+				    const char *name, int index,
+				    u32 *out)
+{
+	const fdt32_t *val;
+	int node_off;
+	int len;
+
+	node_off = fdt_path_offset(fdt, path);
+	if (node_off < 0)
+		return node_off;
+
+	val = fdt_getprop(fdt, node_off, name, &len);
+	if (!val || (len < (sizeof(uint32_t) * (index + 1))))
+		return -FDT_ERR_NOTFOUND;
+
+	*out = fdt32_to_cpu(*(val + index));
+
+	return 0;
+}
+
+static int fdt_getprop_u32(void *fdt, const char *path, const char *name,
+			   u32 *out)
+{
+	return fdt_getprop_u32_by_index(fdt, path, name, 0, out);
+}
+
+static int fdt_getprop_str(void *fdt, const char *path, const char *name,
+			   const char **out)
+{
+	int node_off;
+
+	node_off = fdt_path_offset(fdt, path);
+	if (node_off < 0)
+		return node_off;
+
+	return fdt_get_string(fdt, node_off, name, out);
+}
+
+static int fdt_overlay_change_int_property(struct unit_test_state *uts)
+{
+	void *fdt = uts->priv;
+	u32 val = 0;
+
+	ut_assertok(fdt_getprop_u32(fdt, "/test-node", "test-int-property",
+				    &val));
+	ut_asserteq(43, val);
+
+	return CMD_RET_SUCCESS;
+}
+OVERLAY_TEST(fdt_overlay_change_int_property, 0);
+
+static int fdt_overlay_change_str_property(struct unit_test_state *uts)
+{
+	void *fdt = uts->priv;
+	const char *val = NULL;
+
+	ut_assertok(fdt_getprop_str(fdt, "/test-node", "test-str-property",
+				    &val));
+	ut_asserteq_str("foobar", val);
+
+	return CMD_RET_SUCCESS;
+}
+OVERLAY_TEST(fdt_overlay_change_str_property, 0);
+
+static int fdt_overlay_add_str_property(struct unit_test_state *uts)
+{
+	void *fdt = uts->priv;
+	const char *val = NULL;
+
+	ut_assertok(fdt_getprop_str(fdt, "/test-node", "test-str-property-2",
+				    &val));
+	ut_asserteq_str("foobar2", val);
+
+	return CMD_RET_SUCCESS;
+}
+OVERLAY_TEST(fdt_overlay_add_str_property, 0);
+
+static int fdt_overlay_add_node_by_phandle(struct unit_test_state *uts)
+{
+	void *fdt = uts->priv;
+	int off;
+
+	off = fdt_path_offset(fdt, "/test-node/new-node");
+	ut_assert(off >= 0);
+
+	ut_assertnonnull(fdt_getprop(fdt, off, "new-property", NULL));
+
+	return CMD_RET_SUCCESS;
+}
+OVERLAY_TEST(fdt_overlay_add_node_by_phandle, 0);
+
+static int fdt_overlay_add_node_by_path(struct unit_test_state *uts)
+{
+	void *fdt = uts->priv;
+	int off;
+
+	off = fdt_path_offset(fdt, "/new-node");
+	ut_assert(off >= 0);
+
+	ut_assertnonnull(fdt_getprop(fdt, off, "new-property", NULL));
+
+	return CMD_RET_SUCCESS;
+}
+OVERLAY_TEST(fdt_overlay_add_node_by_path, 0);
+
+static int fdt_overlay_add_subnode_property(struct unit_test_state *uts)
+{
+	void *fdt = uts->priv;
+	int off;
+
+	off = fdt_path_offset(fdt, "/test-node/sub-test-node");
+	ut_assert(off >= 0);
+
+	ut_assertnonnull(fdt_getprop(fdt, off, "sub-test-property", NULL));
+	ut_assertnonnull(fdt_getprop(fdt, off, "new-sub-test-property", NULL));
+
+	return CMD_RET_SUCCESS;
+}
+OVERLAY_TEST(fdt_overlay_add_subnode_property, 0);
+
+static int fdt_overlay_local_phandle(struct unit_test_state *uts)
+{
+	uint32_t local_phandle;
+	void *fdt = uts->priv;
+	u32 val = 0;
+	int off;
+
+	off = fdt_path_offset(fdt, "/new-local-node");
+	ut_assert(off >= 0);
+
+	local_phandle = fdt_get_phandle(fdt, off);
+	ut_assert(local_phandle);
+
+	ut_assertok(fdt_getprop_u32_by_index(fdt, "/", "test-several-phandle",
+					     0, &val));
+	ut_asserteq(local_phandle, val);
+
+	ut_assertok(fdt_getprop_u32_by_index(fdt, "/", "test-several-phandle",
+					     1, &val));
+	ut_asserteq(local_phandle, val);
+
+	return CMD_RET_SUCCESS;
+}
+OVERLAY_TEST(fdt_overlay_local_phandle, 0);
+
+static int fdt_overlay_local_phandles(struct unit_test_state *uts)
+{
+	uint32_t local_phandle, test_phandle;
+	void *fdt = uts->priv;
+	u32 val = 0;
+	int off;
+
+	off = fdt_path_offset(fdt, "/new-local-node");
+	ut_assert(off >= 0);
+
+	local_phandle = fdt_get_phandle(fdt, off);
+	ut_assert(local_phandle);
+
+	off = fdt_path_offset(fdt, "/test-node");
+	ut_assert(off >= 0);
+
+	test_phandle = fdt_get_phandle(fdt, off);
+	ut_assert(test_phandle);
+
+	ut_assertok(fdt_getprop_u32_by_index(fdt, "/", "test-phandle", 0,
+					     &val));
+	ut_asserteq(test_phandle, val);
+
+	ut_assertok(fdt_getprop_u32_by_index(fdt, "/", "test-phandle", 1,
+					     &val));
+	ut_asserteq(local_phandle, val);
+
+	return CMD_RET_SUCCESS;
+}
+OVERLAY_TEST(fdt_overlay_local_phandles, 0);
+
+int do_ut_overlay(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
+{
+	struct unit_test *tests = ll_entry_start(struct unit_test,
+						 overlay_test);
+	const int n_ents = ll_entry_count(struct unit_test, overlay_test);
+	struct unit_test_state *uts;
+	struct unit_test *test;
+	void *fdt_base = &__dtb_test_fdt_base_begin;
+	void *fdt_overlay = &__dtb_test_fdt_overlay_begin;
+	void *fdt_base_copy, *fdt_overlay_copy;
+
+	uts = calloc(1, sizeof(*uts));
+	if (!uts)
+		return -ENOMEM;
+
+	ut_assertok(fdt_check_header(fdt_base));
+	ut_assertok(fdt_check_header(fdt_overlay));
+
+	fdt_base_copy = malloc(FDT_COPY_SIZE);
+	if (!fdt_base_copy)
+		return -ENOMEM;
+	uts->priv = fdt_base_copy;
+
+	fdt_overlay_copy = malloc(FDT_COPY_SIZE);
+	if (!fdt_overlay_copy)
+		return -ENOMEM;
+
+	/*
+	 * Resize the FDT to 4k so that we have room to operate on
+	 *
+	 * (and relocate it since the memory might be mapped
+	 * read-only)
+	 */
+	ut_assertok(fdt_open_into(fdt_base, fdt_base_copy, FDT_COPY_SIZE));
+
+	/*
+	 * Resize the overlay to 4k so that we have room to operate on
+	 *
+	 * (and relocate it since the memory might be mapped
+	 * read-only)
+	 */
+	ut_assertok(fdt_open_into(fdt_overlay, fdt_overlay_copy,
+				  FDT_COPY_SIZE));
+
+	/* Apply the overlay */
+	ut_assertok(fdt_overlay_apply(fdt_base_copy, fdt_overlay_copy));
+
+	if (argc == 1)
+		printf("Running %d environment tests\n", n_ents);
+
+	for (test = tests; test < tests + n_ents; test++) {
+		if (argc > 1 && strcmp(argv[1], test->name))
+			continue;
+		printf("Test: %s\n", test->name);
+
+		uts->start = mallinfo();
+
+		test->func(uts);
+	}
+
+	printf("Failures: %d\n", uts->fail_count);
+
+	free(fdt_overlay_copy);
+	free(fdt_base_copy);
+	free(uts);
+
+	return uts->fail_count ? CMD_RET_FAILURE : 0;
+}
diff --git a/test/overlay/test-fdt-base.dts b/test/overlay/test-fdt-base.dts
new file mode 100644
index 0000000..2603adb
--- /dev/null
+++ b/test/overlay/test-fdt-base.dts
@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) 2016 NextThing Co
+ * Copyright (c) 2016 Free Electrons
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+/dts-v1/;
+
+/ {
+	test: test-node {
+		test-int-property = <42>;
+		test-str-property = "foo";
+
+		subtest: sub-test-node {
+			sub-test-property;
+		};
+	};
+};
+
+
diff --git a/test/overlay/test-fdt-overlay.dts b/test/overlay/test-fdt-overlay.dts
new file mode 100644
index 0000000..d30ecdf
--- /dev/null
+++ b/test/overlay/test-fdt-overlay.dts
@@ -0,0 +1,96 @@
+/*
+ * Copyright (c) 2016 NextThing Co
+ * Copyright (c) 2016 Free Electrons
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+/dts-v1/;
+/plugin/;
+
+/ {
+	/* Test that we can change an int by another */
+	fragment@0 {
+		target = <&test>;
+
+		__overlay__ {
+			test-int-property = <43>;
+		};
+	};
+
+	/* Test that we can replace a string by a longer one */
+	fragment@1 {
+		target = <&test>;
+
+		__overlay__ {
+			test-str-property = "foobar";
+		};
+	};
+
+	/* Test that we add a new property */
+	fragment@2 {
+		target = <&test>;
+
+		__overlay__ {
+			test-str-property-2 = "foobar2";
+		};
+	};
+
+	/* Test that we add a new node (by phandle) */
+	fragment@3 {
+		target = <&test>;
+
+		__overlay__ {
+			new-node {
+				new-property;
+			};
+		};
+	};
+
+	/* Test that we add a new node (by path) */
+	fragment@4 {
+		target-path = "/";
+
+		__overlay__ {
+			new-node {
+				new-property;
+			};
+		};
+	};
+
+	fragment@5 {
+		target-path = "/";
+
+		__overlay__ {
+			local: new-local-node {
+				new-property;
+			};
+		};
+	};
+
+	fragment@6 {
+		target-path = "/";
+
+		__overlay__ {
+			test-phandle = <&test>, <&local>;
+		};
+	};
+
+	fragment@7 {
+		target-path = "/";
+
+		__overlay__ {
+			test-several-phandle = <&local>, <&local>;
+		};
+	};
+
+	fragment@8 {
+		target = <&test>;
+
+		__overlay__ {
+			sub-test-node {
+				new-sub-test-property;
+			};
+		};
+	};
+};