dm: core: Add function to get child count of ofnode or device

This patch add function used to get the child count of
a ofnode or a device

Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Reviewed-by: Weijie Gao <weijie.gao@mediatek.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/include/dm/read.h b/include/dm/read.h
index 03c15b8..b952551 100644
--- a/include/dm/read.h
+++ b/include/dm/read.h
@@ -669,6 +669,14 @@
  */
 int dev_read_alias_highest_id(const char *stem);
 
+/**
+ * dev_get_child_count() - get the child count of a device
+ *
+ * @dev: device to use for interation (struct udevice *)
+ * @return the count of child subnode
+ */
+int dev_get_child_count(const struct udevice *dev);
+
 #else /* CONFIG_DM_DEV_READ_INLINE is enabled */
 
 static inline int dev_read_u32(const struct udevice *dev,
@@ -978,6 +986,11 @@
 	return fdtdec_get_alias_highest_id(gd->fdt_blob, stem);
 }
 
+static inline int dev_get_child_count(const struct udevice *dev)
+{
+	return ofnode_get_child_count(dev_ofnode(dev));
+}
+
 #endif /* CONFIG_DM_DEV_READ_INLINE */
 
 /**