dt-bindings: power: add binding for px30 power domains

Add binding documentation for the power domains
found on Rockchip PX30 SoCs.
Signed-off-by: Finley Xiao <finley.xiao@rock-chips.com>
Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

Documentation/devicetree/bindings/soc/rockchip/power_domain.txt

@@ -5,6 +5,7 @@ powered up/down by software based on different application scenes to save power.
 
 Required properties for power domain controller:
 - compatible: Should be one of the following.
+	"rockchip,px30-power-controller" - for PX30 SoCs.
 	"rockchip,rk3036-power-controller" - for RK3036 SoCs.
 	"rockchip,rk3128-power-controller" - for RK3128 SoCs.
 	"rockchip,rk3228-power-controller" - for RK3228 SoCs.
@@ -20,6 +21,7 @@ Required properties for power domain controller:
 
 Required properties for power domain sub nodes:
 - reg: index of the power domain, should use macros in:
+	"include/dt-bindings/power/px30-power.h" - for PX30 type power domain.
 	"include/dt-bindings/power/rk3036-power.h" - for RK3036 type power domain.
 	"include/dt-bindings/power/rk3128-power.h" - for RK3128 type power domain.
 	"include/dt-bindings/power/rk3228-power.h" - for RK3228 type power domain.
@@ -99,6 +101,7 @@ Node of a device using power domains must have a power-domains property,
 containing a phandle to the power device node and an index specifying which
 power domain to use.
 The index should use macros in:
+	"include/dt-bindings/power/px30-power.h" - for px30 type power domain.
 	"include/dt-bindings/power/rk3036-power.h" - for rk3036 type power domain.
 	"include/dt-bindings/power/rk3128-power.h" - for rk3128 type power domain.
 	"include/dt-bindings/power/rk3128-power.h" - for rk3228 type power domain.