dt-bindings: soc: loongson,ls2k-pmc: Allow syscon-reboot/syscon-poweroff as child

The reboot and poweroff features are actually part of the Power
Management Unit system controller, thus allow them as its children,
instead of specifying as separate device nodes with syscon phandle.

Without it, the reboot/poweroff feature becomes unavailable.

Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

dt-bindings: soc: loongson,ls2k-pmc: Use fallbacks for ls2k-pmc compatible

The Loongson-2K series chips (ls2k0500/ls2k1000/ls2k2000) share the same
PM system controller, using ls2k0500 compatible as fallback for the
others.

Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

soc: dt-bindings: add loongson-2 pm

Add the Loongson-2 SoC Power Management Controller binding with DT
schema format using json-schema.

Signed-off-by: Yinbo Zhu <zhuyinbo@loongson.cn>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230803063703.5659-2-zhuyinbo@loongson.cn
Signed-off-by: Arnd Bergmann <arnd@arndb.de>