Add devicetree binding documentation for the FriendlyARM NanoPi R4S.
Signed-off-by: Tianling Shen <cnsztl@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210319051627.814-1-cnsztl@gmail.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>