staging: media: tegra-video: document tegra_channel_get_remote_source_subdev

Clarify what this function does.
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

drivers/staging/media/tegra-video/vi.c

@@ -164,6 +164,9 @@ tegra_channel_get_remote_csi_subdev(struct tegra_vi_channel *chan)
 	return media_entity_to_v4l2_subdev(pad->entity);
 }
 
+/*
+ * Walk up the chain until the initial source (e.g. image sensor)
+ */
 struct v4l2_subdev *
 tegra_channel_get_remote_source_subdev(struct tegra_vi_channel *chan)
 {