dt-bindings: soc: socionext: Add UniPhier SoC-glue logic

dt-bindings: soc: socionext: Add UniPhier SoC-glue logic

Add devicetree binding schema for the SoC-glue logic implemented on
Socionext Uniphier SoCs.

This SoC-glue logic is a set of miscellaneous function registers
handling signals for specific devices outside system components,
and also has multiple functions such as I/O pinmux, usb-phy, debug,
clock-mux for a specific SoC, and so on.

Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20221213082449.2721-11-hayashi.kunihiko@socionext.com
Signed-off-by: Rob Herring <robh@kernel.org>