V4L/DVB (9209): v4l2: add comment to the v4l2-i2c-drv headers.

Looking at these headers as they appear in the kernel makes you
wonder why it is done that way. Refer to the v4l-dvb repository
where the full unstripped header can be found to understand the
reasoning behind this.
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

include/media/v4l2-i2c-drv-legacy.h

@@ -21,6 +21,17 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+/* NOTE: the full version of this header is in the v4l-dvb repository
+ * and allows v4l i2c drivers to be compiled on older kernels as well.
+ * The version of this header as it appears in the kernel is a stripped
+ * version (without all the backwards compatibility stuff) and so it
+ * looks a bit odd.
+ *
+ * If you look at the full version then you will understand the reason
+ * for introducing this header since you really don't want to have all
+ * the tricky backwards compatibility code in each and every i2c driver.
+ */
+
 struct v4l2_i2c_driver_data {
 	const char * const name;
 	int driverid;

include/media/v4l2-i2c-drv.h

@@ -21,6 +21,17 @@
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
 
+/* NOTE: the full version of this header is in the v4l-dvb repository
+ * and allows v4l i2c drivers to be compiled on older kernels as well.
+ * The version of this header as it appears in the kernel is a stripped
+ * version (without all the backwards compatibility stuff) and so it
+ * looks a bit odd.
+ *
+ * If you look at the full version then you will understand the reason
+ * for introducing this header since you really don't want to have all
+ * the tricky backwards compatibility code in each and every i2c driver.
+ */
+
 #ifndef __V4L2_I2C_DRV_H__
 #define __V4L2_I2C_DRV_H__