of: Add for_each_endpoint_of_node helper macro

Note that while of_graph_get_next_endpoint decrements the reference count
of the child node passed to it, of_node_put(child) still has to be called
manually when breaking out of the loop.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

include/linux/of_graph.h

@@ -26,6 +26,17 @@ struct of_endpoint {
 	const struct device_node *local_node;
 };
 
+/**
+ * for_each_endpoint_of_node - iterate over every endpoint in a device node
+ * @parent: parent device node containing ports and endpoints
+ * @child: loop variable pointing to the current endpoint node
+ *
+ * When breaking out of the loop, of_node_put(child) has to be called manually.
+ */
+#define for_each_endpoint_of_node(parent, child) \
+	for (child = of_graph_get_next_endpoint(parent, NULL); child != NULL; \
+	     child = of_graph_get_next_endpoint(parent, child))
+
 #ifdef CONFIG_OF
 int of_graph_parse_endpoint(const struct device_node *node,
 				struct of_endpoint *endpoint);