Add dt binding documentation for rockchip display port PHY.
Signed-off-by: NYakir Yang <ykk@rock-chips.com>
Acked-by: NRob Herring <robh@kernel.org>
Reviewed-by: NHeiko Stuebner <heiko@sntech.de>
Signed-off-by: NKishon Vijay Abraham I <kishon@ti.com>