media: video-mux: Skip dangling endpoints

i.MX6 device tree include files contain dangling endpoints for the
board device tree writers' convenience. These are still included in
many existing device trees.
Treat dangling endpoints as non-existent to support them.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Fixes: 612b385e ("media: video-mux: Create media links in bound notifier")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/platform/video-mux.c

@@ -364,7 +364,7 @@ static int video_mux_async_register(struct video_mux *vmux,
 
 	for (i = 0; i < num_input_pads; i++) {
 		struct v4l2_async_subdev *asd;
-		struct fwnode_handle *ep;
+		struct fwnode_handle *ep, *remote_ep;
 
 		ep = fwnode_graph_get_endpoint_by_id(
 			dev_fwnode(vmux->subdev.dev), i, 0,
@@ -372,6 +372,14 @@ static int video_mux_async_register(struct video_mux *vmux,
 		if (!ep)
 			continue;
 
+		/* Skip dangling endpoints for backwards compatibility */
+		remote_ep = fwnode_graph_get_remote_endpoint(ep);
+		if (!remote_ep) {
+			fwnode_handle_put(ep);
+			continue;
+		}
+		fwnode_handle_put(remote_ep);
+
 		asd = v4l2_async_notifier_add_fwnode_remote_subdev(
 			&vmux->notifier, ep, struct v4l2_async_subdev);