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+Rockchip RK3328 GRF (General Register Files) GPIO controller.
+
+In Rockchip RK3328, the output only GPIO_MUTE pin, originally for codec mute
+control, can also be used for general purpose. It is manipulated by the
+GRF_SOC_CON10 register in GRF. Aside from the GPIO_MUTE pin, the HDMI pins can
+also be set in the same way.
+
+Currently this GPIO controller only supports the mute pin. If needed in the
+future, the HDMI pins support can also be added.
+
+Required properties:
+- compatible: Should contain "rockchip,rk3328-grf-gpio".
+- gpio-controller: Marks the device node as a gpio controller.
+- #gpio-cells: Should be 2. The first cell is the pin number and
+ the second cell is used to specify the gpio polarity:
+ 0 = Active high,
+ 1 = Active low.
+
+Example:
+
+ grf: syscon@ff100000 {
+ compatible = "rockchip,rk3328-grf", "syscon", "simple-mfd";
+
+ grf_gpio: grf-gpio {
+ compatible = "rockchip,rk3328-grf-gpio";
+ gpio-controller;
+ #gpio-cells = <2>;
+ };
+ };
+
+Note: The grf_gpio node should be declared as the child of the GRF (General
+Register File) node. The GPIO_MUTE pin is referred to as <&grf_gpio 0>.