gpio: mmio: add support for NI 169445 NAND GPIO

The GPIO-based NAND controller on National Instruments 169445 hardware
exposes a set of simple lines for the control signals.

Signed-off-by: Nathan Sullivan <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

Documentation/devicetree/bindings/gpio/ni,169445-nand-gpio.txt

···
+Bindings for the National Instruments 169445 GPIO NAND controller
+
+The 169445 GPIO NAND controller has two memory mapped GPIO registers, one
+for input (the ready signal) and one for output (control signals).  It is
+intended to be used with the GPIO NAND driver.
+
+Required properties:
+	- compatible: should be "ni,169445-nand-gpio"
+	- reg-names: must contain
+		"dat" - data register
+	- reg: address + size pairs describing the GPIO register sets;
+		order must correspond with the order of entries in reg-names
+	- #gpio-cells: must be set to 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
+	- gpio-controller: Marks the device node as a gpio controller.
+
+Optional properties:
+	- no-output: disables driving output on the pins
+
+Examples:
+	gpio1: nand-gpio-out@1f300010 {
+		compatible = "ni,169445-nand-gpio";
+		reg = <0x1f300010 0x4>;
+		reg-names = "dat";
+		gpio-controller;
+		#gpio-cells = <2>;
+	};
+
+	gpio2: nand-gpio-in@1f300014 {
+		compatible = "ni,169445-nand-gpio";
+		reg = <0x1f300014 0x4>;
+		reg-names = "dat";
+		gpio-controller;
+		#gpio-cells = <2>;
+		no-output;
+	};

drivers/gpio/gpio-mmio.c

···
 static const struct of_device_id bgpio_of_match[] = {
 	{ .compatible = "brcm,bcm6345-gpio" },
 	{ .compatible = "wd,mbl-gpio" },
+	{ .compatible = "ni,169445-nand-gpio" },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, bgpio_of_match);