[media] videodev2.h: Make V4L2_PIX_FMT_MPEG4 comment more specific about its usage

Signed-off-by: Ismael Luceno <ismael.luceno@corp.bluecherry.net>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

include/uapi/linux/videodev2.h

@@ -395,7 +395,7 @@ struct v4l2_pix_format {
 #define V4L2_PIX_FMT_H263     v4l2_fourcc('H', '2', '6', '3') /* H263          */
 #define V4L2_PIX_FMT_MPEG1    v4l2_fourcc('M', 'P', 'G', '1') /* MPEG-1 ES     */
 #define V4L2_PIX_FMT_MPEG2    v4l2_fourcc('M', 'P', 'G', '2') /* MPEG-2 ES     */
-#define V4L2_PIX_FMT_MPEG4    v4l2_fourcc('M', 'P', 'G', '4') /* MPEG-4 ES     */
+#define V4L2_PIX_FMT_MPEG4    v4l2_fourcc('M', 'P', 'G', '4') /* MPEG-4 part 2 ES */
 #define V4L2_PIX_FMT_XVID     v4l2_fourcc('X', 'V', 'I', 'D') /* Xvid           */
 #define V4L2_PIX_FMT_VC1_ANNEX_G v4l2_fourcc('V', 'C', '1', 'G') /* SMPTE 421M Annex G compliant stream */
 #define V4L2_PIX_FMT_VC1_ANNEX_L v4l2_fourcc('V', 'C', '1', 'L') /* SMPTE 421M Annex L compliant stream */