dt-bindings: add document of Rockchip power domains

This add the necessary binding documentation for the power domains
found on Rockchip SoCs.

Signed-off-by: Caesar Wang <wxt@rock-chips.com>
Reviewed-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

diff --git a/Documentation/devicetree/bindings/soc/rockchip/power_domain.txt b/Documentation/devicetree/bindings/soc/rockchip/power_domain.txt
new file mode 100644 (file)
index 0000000..4be3418
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+++ b/Documentation/devicetree/bindings/soc/rockchip/power_domain.txt
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+* Rockchip Power Domains
+
+Rockchip processors include support for multiple power domains which can be
+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.
+- #power-domain-cells: Number of cells in a power-domain specifier.
+       Should be 1 for multiple PM domains.
+- #address-cells: Should be 1.
+- #size-cells: Should be 0.
+
+Required properties for power domain sub nodes:
+- reg: index of the power domain, should use macros in:
+       "include/dt-bindings/power-domain/rk3288.h" - for RK3288 type power domain.
+- clocks (optional): phandles to clocks which need to be enabled while power domain
+       switches state.
+
+Example:
+
+       power: power-controller {
+               compatible = "rockchip,rk3288-power-controller";
+               #power-domain-cells = <1>;
+               #address-cells = <1>;
+               #size-cells = <0>;
+
+               pd_gpu {
+                       reg = <RK3288_PD_GPU>;
+                       clocks = <&cru ACLK_GPU>;
+               };
+       };
+
+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-domain/rk3288.h" - for rk3288 type power domain.
+
+Example of the node using power domain:
+
+       node {
+               /* ... */
+               power-domains = <&power RK3288_PD_GPU>;
+               /* ... */
+       };