dm: core: Add a way to find a device by its driver

Some SoCs have a single clock device. Provide a way to find it given its
driver name. This is handled by the linker so will fail if the name is not
found, avoiding strange errors when names change and do not match. It is
also faster than a string comparison.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/core/uclass.c b/drivers/core/uclass.c
index 1141ce1..de602ae 100644
--- a/drivers/core/uclass.c
+++ b/drivers/core/uclass.c
@@ -311,6 +311,26 @@
 }
 #endif
 
+int uclass_get_device_by_driver(enum uclass_id id,
+				const struct driver *find_drv,
+				struct udevice **devp)
+{
+	struct udevice *dev;
+	struct uclass *uc;
+	int ret;
+
+	ret = uclass_get(id, &uc);
+	if (ret)
+		return ret;
+
+	list_for_each_entry(dev, &uc->dev_head, uclass_node) {
+		if (dev->driver == find_drv)
+			return uclass_get_device_tail(dev, 0, devp);
+	}
+
+	return -ENODEV;
+}
+
 int uclass_get_device_tail(struct udevice *dev, int ret,
 				  struct udevice **devp)
 {