Add documentation for ad5820 device tree binding.
Signed-off-by: NPavel Machek <pavel@denx.de>
Acked-by: NRob Herring <robh@kernel.org>
Signed-off-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>