dt-bindings: add binding for rk3328 power domains

Add binding documentation for the power domains
found on Rockchip RK3328 SoCs.
But RK3328 SoC just support idle, not support pd.
Signed-off-by: Elaine Zhang <zhangqing@rock-chips.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

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

@@ -6,6 +6,7 @@ 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,rk3288-power-controller" - for RK3288 SoCs.
+	"rockchip,rk3328-power-controller" - for RK3328 SoCs.
 	"rockchip,rk3368-power-controller" - for RK3368 SoCs.
 	"rockchip,rk3399-power-controller" - for RK3399 SoCs.
 - #power-domain-cells: Number of cells in a power-domain specifier.
@@ -16,6 +17,7 @@ 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/rk3288-power.h" - for RK3288 type power domain.
+	"include/dt-bindings/power/rk3328-power.h" - for RK3328 type power domain.
 	"include/dt-bindings/power/rk3368-power.h" - for RK3368 type power domain.
 	"include/dt-bindings/power/rk3399-power.h" - for RK3399 type power domain.
 - clocks (optional): phandles to clocks which need to be enabled while power domain
@@ -90,6 +92,7 @@ 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/rk3288-power.h" - for rk3288 type power domain.
+	"include/dt-bindings/power/rk3328-power.h" - for rk3328 type power domain.
 	"include/dt-bindings/power/rk3368-power.h" - for rk3368 type power domain.
 	"include/dt-bindings/power/rk3399-power.h" - for rk3399 type power domain.