gpio: dt-bindings: Add documentation for gpio controllers on Armada 7K/8K

Document the device tree binding for the gpio controllers found on the
Marvell Armada 7K and Armada 8K SoCs.

Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Gregory CLEMENT <[e-mail]>

Documentation/devicetree/bindings/arm/marvell/ap806-system-controller.txt

···
 mpp18	18	gpio
 mpp19	19	gpio, uart0(rxd), sdio(pw_off)
 
+GPIO:
+-----
+For common binding part and usage, refer to
+Documentation/devicetree/bindings/gpio/gpio-mvebu.txt.
+
+Required properties:
+
+- compatible: "marvell,armada-8k-gpio"
+
+- offset: offset address inside the syscon block
+
 Example:
 ap_syscon: system-controller@6f4000 {
 	compatible = "syscon", "simple-mfd";
···
 
 	ap_pinctrl: pinctrl {
 		compatible = "marvell,ap806-pinctrl";
+	};
+
+	ap_gpio: gpio {
+		compatible = "marvell,armada-8k-gpio";
+		offset = <0x1040>;
+		ngpios = <19>;
+		gpio-controller;
+		#gpio-cells = <2>;
+		gpio-ranges = <&ap_pinctrl 0 0 19>;
 	};
 };

Documentation/devicetree/bindings/arm/marvell/cp110-system-controller0.txt

···
 mpp61	61	gpio, mss_gpio5, ptp(clk), tdm(pclk), au(i2sextclk), spi0(csn2), uart0(txd), uart2(txd), sata1(present_act), ge(mdio), sdio(d3)
 mpp62	62	gpio, mss_gpio4, synce1(clk), ptp(pclk_out), sata1(present_act), spi0(csn3), uart0(rxd), uart2(rxd), sata0(present_act), ge(mdc)
 
+GPIO:
+-----
+
+For common binding part and usage, refer to
+Documentation/devicetree/bindings/gpio/gpio-mvebu.txt.
+
+Required properties:
+
+- compatible: "marvell,armada-8k-gpio"
+
+- offset: offset address inside the syscon block
+
 Example:
 
 cpm_syscon0: system-controller@440000 {
···
 	cpm_pinctrl: pinctrl {
 		compatible = "marvell,armada-8k-cpm-pinctrl";
 	};
-};
 
+	cpm_gpio1: gpio@100 {
+		compatible = "marvell,armada-8k-gpio";
+		offset = <0x100>;
+		ngpios = <32>;
+		gpio-controller;
+		#gpio-cells = <2>;
+		gpio-ranges = <&cpm_pinctrl 0 0 32>;
+		status = "disabled";
+	};
+
+};

Documentation/devicetree/bindings/gpio/gpio-mvebu.txt

···
 
 Required properties:
 
-- compatible : Should be "marvell,orion-gpio", "marvell,mv78200-gpio"
-  or "marvell,armadaxp-gpio". "marvell,orion-gpio" should be used for
-  Orion, Kirkwood, Dove, Discovery (except MV78200) and Armada
-  370. "marvell,mv78200-gpio" should be used for the Discovery
-  MV78200. "marvel,armadaxp-gpio" should be used for all Armada XP
-  SoCs (MV78230, MV78260, MV78460).
+- compatible : Should be "marvell,orion-gpio", "marvell,mv78200-gpio",
+  "marvell,armadaxp-gpio" or "marvell,armada-8k-gpio".
+
+    "marvell,orion-gpio" should be used for Orion, Kirkwood, Dove,
+    Discovery (except MV78200) and Armada 370. "marvell,mv78200-gpio"
+    should be used for the Discovery MV78200.
+
+    "marvel,armadaxp-gpio" should be used for all Armada XP SoCs
+    (MV78230, MV78260, MV78460).
+
+    "marvell,armada-8k-gpio" should be used for the Armada 7K and 8K
+    SoCs (either from AP or CP), see
+    Documentation/devicetree/bindings/arm/marvell/cp110-system-controller0.txt
+    and
+    Documentation/devicetree/bindings/arm/marvell/ap806-system-controller.txt
+    for specific details about the offset property.
 
 - reg: Address and length of the register set for the device. Only one
   entry is expected, except for the "marvell,armadaxp-gpio" variant
   for which two entries are expected: one for the general registers,
-  one for the per-cpu registers.
+  one for the per-cpu registers. Not used for marvell,armada-8k-gpio.
 
 - interrupts: The list of interrupts that are used for all the pins
   managed by this GPIO bank. There can be more than one interrupt