dt-bindings: Add Oxford Semiconductor OXNAS pinctrl and gpio bindings

Add pinctrl and gpio DT bindings for Oxford Semiconductor OXNAS SoC Family.
This version supports the ARM926EJ-S based OX810SE SoC with 34 IO pins.
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/gpio/gpio_oxnas.txt

+* Oxford Semiconductor OXNAS SoC GPIO Controller
+
+Please refer to gpio.txt for generic information regarding GPIO bindings.
+
+Required properties:
+ - compatible: "oxsemi,ox810se-gpio"
+ - reg: Base address and length for the device.
+ - interrupts: The port interrupt shared by all pins.
+ - gpio-controller: Marks the port as GPIO controller.
+ - #gpio-cells: Two. The first cell is the pin number and
+   the second cell is used to specify the gpio polarity as defined in
+   defined in <dt-bindings/gpio/gpio.h>:
+      0 = GPIO_ACTIVE_HIGH
+      1 = GPIO_ACTIVE_LOW
+ - interrupt-controller: Marks the device node as an interrupt controller.
+ - #interrupt-cells: Two. The first cell is the GPIO number and second cell
+   is used to specify the trigger type as defined in
+   <dt-bindings/interrupt-controller/irq.h>:
+      IRQ_TYPE_EDGE_RISING
+      IRQ_TYPE_EDGE_FALLING
+      IRQ_TYPE_EDGE_BOTH
+ - gpio-ranges: Interaction with the PINCTRL subsystem, it also specifies the
+   gpio base and count, should be in the format of numeric-gpio-range as
+   specified in the gpio.txt file.
+
+Example:
+
+gpio0: gpio@0 {
+	compatible = "oxsemi,ox810se-gpio";
+	reg = <0x000000 0x100000>;
+	interrupts = <21>;
+	#gpio-cells = <2>;
+	gpio-controller;
+	interrupt-controller;
+	#interrupt-cells = <2>;
+	gpio-ranges = <&pinctrl 0 0 32>;
+};
+
+keys {
+	...
+
+	button-esc {
+		label = "ESC";
+		linux,code = <1>;
+		gpios = <&gpio0 12 0>;
+	};
+};

Documentation/devicetree/bindings/pinctrl/oxnas,pinctrl.txt

+* Oxford Semiconductor OXNAS SoC Family Pin Controller
+
+Please refer to pinctrl-bindings.txt, ../gpio/gpio.txt, and
+../interrupt-controller/interrupts.txt for generic information regarding
+pin controller, GPIO, and interrupt bindings.
+
+OXNAS 'pin configuration node' is a node of a group of pins which can be
+used for a specific device or function. This node represents configurations of
+pins, optional function, and optional mux related configuration.
+
+Required properties for pin controller node:
+ - compatible: "oxsemi,ox810se-pinctrl"
+ - oxsemi,sys-ctrl: a phandle to the system controller syscon node
+
+Required properties for pin configuration sub-nodes:
+ - pins: List of pins to which the configuration applies.
+
+Optional properties for pin configuration sub-nodes:
+----------------------------------------------------
+ - function: Mux function for the specified pins.
+ - bias-pull-up: Enable weak pull-up.
+
+Example:
+
+pinctrl: pinctrl {
+	compatible = "oxsemi,ox810se-pinctrl";
+
+	/* Regmap for sys registers */
+	oxsemi,sys-ctrl = <&sys>;
+
+	pinctrl_uart2: pinctrl_uart2 {
+		uart2a {
+			pins = "gpio31";
+			function = "fct3";
+		};
+		uart2b {
+			pins = "gpio32";
+			function = "fct3";
+		};
+	};
+};
+
+uart2: serial@900000 {
+	compatible = "ns16550a";
+	reg = <0x900000 0x100000>;
+	clocks = <&sysclk>;
+	interrupts = <29>;
+	reg-shift = <0>;
+	fifo-size = <16>;
+	reg-io-width = <1>;
+	current-speed = <115200>;
+	no-loopback-test;
+	status = "disabled";
+	resets = <&reset 22>;
+	pinctrl-names = "default";
+	pinctrl-0 = <&pinctrl_uart2>;
+};