[media] videodev2.h: add V4L2_FIELD_HAS_T_OR_B macro

Add a macro to test if the field consists of a single top
or bottom field. Anyone who needs to work with fields as opposed to
frame will need this.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

include/uapi/linux/videodev2.h

@@ -124,6 +124,10 @@ enum v4l2_field {
 	 (field) == V4L2_FIELD_INTERLACED_BT ||\
 	 (field) == V4L2_FIELD_SEQ_TB ||\
 	 (field) == V4L2_FIELD_SEQ_BT)
+#define V4L2_FIELD_HAS_T_OR_B(field)	\
+	((field) == V4L2_FIELD_BOTTOM ||\
+	 (field) == V4L2_FIELD_TOP ||\
+	 (field) == V4L2_FIELD_ALTERNATE)
 
 enum v4l2_buf_type {
 	V4L2_BUF_TYPE_VIDEO_CAPTURE        = 1,