docs: dt-bindings: add DTS Coding Style document

docs: dt-bindings: add DTS Coding Style document

Document preferred coding style for Devicetree sources (DTS and DTSI),
to bring consistency among all (sub)architectures and ease in reviews.

Cc: Andrew Davis <afd@ti.com>
cc: Andrew Lunn <andrew@lunn.ch>
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bjorn Andersson <andersson@kernel.org>
Cc: Chen-Yu Tsai <wens@kernel.org>
Cc: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: Michal Simek <michal.simek@amd.com>
Cc: Neil Armstrong <neil.armstrong@linaro.org>
Cc: Nishanth Menon <nm@ti.com>
Cc: Olof Johansson <olof@lixom.net>
Cc: Rafał Miłecki <zajec5@gmail.com>
Acked-by: Neil Armstrong <neil.armstrong@linaro.org>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Konrad Dybcio <konradybcio@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://lore.kernel.org/r/20231203174622.18402-1-krzysztof.kozlowski@linaro.org
[robh: quote property names in order of properties section]
Signed-off-by: Rob Herring <robh@kernel.org>