dm: core: Add a function to find any device from device tree

In some rare cases it is useful to be able to locate a device given a device
tree node offset. An example is when you have an alias that points to a node
and you want to find the associated device. The device may be SPI, MMC or
something else, but you don't need to know the uclass to find it.

Add a function to do a global search for a device, given its device tree
offset.

Signed-off-by: Simon Glass <sjg@chromium.org>

drivers/core/device.c

@@ -470,6 +470,31 @@ int device_get_child_by_of_offset(struct udevice *parent, int seq,
 	return device_get_device_tail(dev, ret, devp);
 }
 
+static struct udevice *_device_find_global_by_of_offset(struct udevice *parent,
+							int of_offset)
+{
+	struct udevice *dev, *found;
+
+	if (parent->of_offset == of_offset)
+		return parent;
+
+	list_for_each_entry(dev, &parent->child_head, sibling_node) {
+		found = _device_find_global_by_of_offset(dev, of_offset);
+		if (found)
+			return found;
+	}
+
+	return NULL;
+}
+
+int device_get_global_by_of_offset(int of_offset, struct udevice **devp)
+{
+	struct udevice *dev;
+
+	dev = _device_find_global_by_of_offset(gd->dm_root, of_offset);
+	return device_get_device_tail(dev, dev ? 0 : -ENOENT, devp);
+}
+
 int device_find_first_child(struct udevice *parent, struct udevice **devp)
 {
 	if (list_empty(&parent->child_head)) {

include/dm/device.h

@@ -390,6 +390,20 @@ int device_get_child_by_of_offset(struct udevice *parent, int seq,
 				  struct udevice **devp);
 
 /**
+ * device_get_global_by_of_offset() - Get a device based on FDT offset
+ *
+ * Locates a device by its device tree offset, searching globally throughout
+ * the all driver model devices.
+ *
+ * The device is probed to activate it ready for use.
+ *
+ * @of_offset: Device tree offset to find
+ * @devp: Returns pointer to device if found, otherwise this is set to NULL
+ * @return 0 if OK, -ve on error
+ */
+int device_get_global_by_of_offset(int of_offset, struct udevice **devp);
+
+/**
  * device_find_first_child() - Find the first child of a device
  *
  * @parent: Parent device to search