media: ad5820: DT new compatible devices

Document new compatible devices.

Cc: devicetree@vger.kernel.org
Signed-off-by: NRicardo Ribalda Delgado <ribalda@kernel.org>
Reviewed-by: NRob Herring <robh@kernel.org>
Acked-by: NPavel Machek <pavel@ucw.cz>
Signed-off-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab+samsung@kernel.org>

Documentation/devicetree/bindings/media/i2c/ad5820.txt

@@ -2,7 +2,10 @@
 
 Required Properties:
 
-  - compatible: Must contain "adi,ad5820"
+  - compatible: Must contain one of:
+		- "adi,ad5820"
+		- "adi,ad5821"
+		- "adi,ad5823"
 
   - reg: I2C slave address