The media kAPI has two global variables at v4l2-ioctl.h. Document
them.

Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
---
 include/media/v4l2-ioctl.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
index 6f7a58350441..54c83b18d555 100644
--- a/include/media/v4l2-ioctl.h
+++ b/include/media/v4l2-ioctl.h
@@ -663,7 +663,22 @@ void v4l_printk_ioctl(const char *prefix, unsigned int cmd);
 struct video_device;
 
 /* names for fancy debug output */
+
+/**
+ * var v4l2_field_names - Helper array mapping ``V4L2_FIELD_*`` to strings.
+ *
+ * Specially when printing debug messages, it is interesting to output
+ * the field order at the V4L2 buffers. This array associates all possible
+ * values of field pix format from V4L2 API into a string.
+ */
 extern const char *v4l2_field_names[];
+
+/**
+ * var v4l2_type_names - Helper array mapping ``V4L2_BUF_TYPE_*`` to strings.
+ *
+ * When printing debug messages, it is interesting to output the V4L2 buffer
+ * type number with a name that represents its content.
+ */
 extern const char *v4l2_type_names[];
 
 #ifdef CONFIG_COMPAT
-- 
2.52.0