Documentation: dt: wireless: Add wl1251

Add device tree binding documentation for Texas Instrument's wl1251
wireless lan chip. For now only the SPI binding is documented.
Signed-off-by: NSebastian Reichel <sre@debian.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

Documentation/devicetree/bindings/net/wireless/ti,wl1251.txt

+* Texas Instruments wl1251 wireless lan controller
+
+The wl1251 chip can be connected via SPI or via SDIO. This
+document describes the binding for the SPI connected chip.
+
+Required properties:
+- compatible :        Should be "ti,wl1251"
+- reg :               Chip select address of device
+- spi-max-frequency : Maximum SPI clocking speed of device in Hz
+- interrupts :        Should contain interrupt line
+- interrupt-parent :  Should be the phandle for the interrupt controller
+                      that services interrupts for this device
+- vio-supply :        phandle to regulator providing VIO
+- ti,power-gpio :     GPIO connected to chip's PMEN pin
+
+Optional properties:
+- ti,wl1251-has-eeprom : boolean, the wl1251 has an eeprom connected, which
+                         provides configuration data (calibration, MAC, ...)
+- Please consult Documentation/devicetree/bindings/spi/spi-bus.txt
+  for optional SPI connection related properties,
+
+Examples:
+
+&spi1 {
+	wl1251@0 {
+		compatible = "ti,wl1251";
+
+		reg = <0>;
+		spi-max-frequency = <48000000>;
+		spi-cpol;
+		spi-cpha;
+
+		interrupt-parent = <&gpio2>;
+		interrupts = <10 IRQ_TYPE_NONE>; /* gpio line 42 */
+
+		vio-supply = <&vio>;
+		ti,power-gpio = <&gpio3 23 GPIO_ACTIVE_HIGH>; /* 87 */
+	};
+};