net: phy: dp83867: Add device tree bindings and documentation

Add the device tree bindings and the accompanying documentation
for the TI DP83867 Giga bit ethernet phy driver.

The original document was from:
    [commit 2a10154abcb75ad0d7b6bfea6210ac743ec60897 from the Linux kernel]

Signed-off-by: Dan Murphy <dmurphy@ti.com>
Reviewed-by: Mugunthan V N <mugunthanvnm@ti.com>
Tested-by: Mugunthan V N <mugunthanvnm@ti.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/include/dt-bindings/net/ti-dp83867.h b/include/dt-bindings/net/ti-dp83867.h
new file mode 100644
index 0000000..1843757
--- /dev/null
+++ b/include/dt-bindings/net/ti-dp83867.h
@@ -0,0 +1,35 @@
+/*
+ * TI DP83867 PHY drivers
+ *
+ * SPDX-License-Identifier:	GPL-2.0
+ *
+ */
+
+#ifndef _DT_BINDINGS_TI_DP83867_H
+#define _DT_BINDINGS_TI_DP83867_H
+
+/* PHY CTRL bits */
+#define DP83867_PHYCR_FIFO_DEPTH_3_B_NIB	0x00
+#define DP83867_PHYCR_FIFO_DEPTH_4_B_NIB	0x01
+#define DP83867_PHYCR_FIFO_DEPTH_6_B_NIB	0x02
+#define DP83867_PHYCR_FIFO_DEPTH_8_B_NIB	0x03
+
+/* RGMIIDCTL internal delay for rx and tx */
+#define DP83867_RGMIIDCTL_250_PS	0x0
+#define DP83867_RGMIIDCTL_500_PS	0x1
+#define DP83867_RGMIIDCTL_750_PS	0x2
+#define DP83867_RGMIIDCTL_1_NS		0x3
+#define DP83867_RGMIIDCTL_1_25_NS	0x4
+#define DP83867_RGMIIDCTL_1_50_NS	0x5
+#define DP83867_RGMIIDCTL_1_75_NS	0x6
+#define DP83867_RGMIIDCTL_2_00_NS	0x7
+#define DP83867_RGMIIDCTL_2_25_NS	0x8
+#define DP83867_RGMIIDCTL_2_50_NS	0x9
+#define DP83867_RGMIIDCTL_2_75_NS	0xa
+#define DP83867_RGMIIDCTL_3_00_NS	0xb
+#define DP83867_RGMIIDCTL_3_25_NS	0xc
+#define DP83867_RGMIIDCTL_3_50_NS	0xd
+#define DP83867_RGMIIDCTL_3_75_NS	0xe
+#define DP83867_RGMIIDCTL_4_00_NS	0xf
+
+#endif