pinctrl: add DT bindings for lpc1850-scu pinctrl driver

Signed-off-by: Joachim Eastwood <manabian@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Documentation/devicetree/bindings/pinctrl/nxp,lpc1850-scu.txt

+NXP LPC18xx/43xx SCU pin controller Device Tree Bindings
+--------------------------------------------------------
+
+Required properties:
+- compatible		: Should be "nxp,lpc1850-scu"
+- reg			: Address and length of the register set for the device
+- clocks		: Clock specifier (see clock bindings for details)
+
+The lpc1850-scu driver uses the generic pin multiplexing and generic pin
+configuration documented in pinctrl-bindings.txt.
+
+The following generic nodes are supported:
+ - function
+ - pins
+ - bias-disable
+ - bias-pull-up
+ - bias-pull-down
+ - drive-strength
+ - input-enable
+ - input-disable
+ - input-schmitt-enable
+ - input-schmitt-disable
+ - slew-rate
+
+Not all pins support all properties so either refer to the NXP 1850/4350
+user manual or the pin table in the pinctrl-lpc18xx driver for supported
+pin properties.
+
+Example:
+pinctrl: pinctrl@40086000 {
+	compatible = "nxp,lpc1850-scu";
+	reg = <0x40086000 0x1000>;
+	clocks = <&ccu1 CLK_CPU_SCU>;
+
+	i2c0_pins: i2c0-pins {
+		i2c0_pins_cfg {
+			pins = "i2c0_scl", "i2c0_sda";
+			function = "i2c0";
+			input-enable;
+		};
+	};
+
+	uart0_pins: uart0-pins {
+		uart0_rx_cfg {
+			pins = "pf_11";
+			function = "uart0";
+			bias-disable;
+			input-enable;
+		};
+
+		uart0_tx_cfg {
+			pins = "pf_10";
+			function = "uart0";
+			bias-disable;
+		};
+	};
+};