diff --git a/include/uapi/drm/v3d_drm.h b/include/uapi/drm/v3d_drm.h
index 7b6627783608..f446656d00b1 100644
--- a/include/uapi/drm/v3d_drm.h
+++ b/include/uapi/drm/v3d_drm.h
@@ -58,6 +58,11 @@ struct drm_v3d_submit_cl {
 	 * coordinate shader to determine where primitives land on the screen,
 	 * then writes out the state updates and draw calls necessary per tile
 	 * to the tile allocation BO.
+	 *
+	 * This BCL will block on any previous BCL submitted on the
+	 * same FD, but not on any RCL or BCLs submitted by other
+	 * clients -- that is left up to the submitter to control
+	 * using in_sync_bcl if necessary.
 	 */
 	__u32 bcl_start;
 
@@ -69,6 +74,11 @@ struct drm_v3d_submit_cl {
 	 * This is the second set of commands executed, which will either
 	 * execute the tiles that have been set up by the BCL, or a fixed set
 	 * of tiles (in the case of RCL-only blits).
+	 *
+	 * This RCL will block on this submit's BCL, and any previous
+	 * RCL submitted on the same FD, but not on any RCL or BCLs
+	 * submitted by other clients -- that is left up to the
+	 * submitter to control using in_sync_rcl if necessary.
 	 */
 	__u32 rcl_start;