dt: bindings: add TI's wilink wireless device

Add device tree binding documentation for TI's wilink
(wl12xx and wl18xx) wlan chip.
Signed-off-by: Eliad Peller <eliad@wizery.com>
Tested-by: Nikita Kiryanov <nikita@compulab.co.il>
Acked-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>

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

+TI Wilink 6/7/8 (wl12xx/wl18xx) SDIO devices
+
+This node provides properties for controlling the wilink wireless device. The
+node is expected to be specified as a child node to the SDIO controller that
+connects the device to the system.
+
+Required properties:
+ - compatible: should be one of the following:
+    * "ti,wl1271"
+    * "ti,wl1273"
+    * "ti,wl1281"
+    * "ti,wl1283"
+    * "ti,wl1801"
+    * "ti,wl1805"
+    * "ti,wl1807"
+    * "ti,wl1831"
+    * "ti,wl1835"
+    * "ti,wl1837"
+ - interrupts : specifies attributes for the out-of-band interrupt.
+
+Optional properties:
+ - interrupt-parent : the phandle for the interrupt controller to which the
+	device interrupts are connected.
+ - ref-clock-frequency : ref clock frequency in Hz
+ - tcxo-clock-frequency : tcxo clock frequency in Hz
+
+Note: the *-clock-frequency properties assume internal clocks. In case of external
+clock, new bindings (for parsing the clock nodes) have to be added.
+
+Example:
+
+&mmc3 {
+	status = "okay";
+	vmmc-supply = <&wlan_en_reg>;
+	bus-width = <4>;
+	cap-power-off-card;
+	keep-power-in-suspend;
+
+	#address-cells = <1>;
+	#size-cells = <0>;
+	wlcore: wlcore@2 {
+		compatible = "ti,wl1835";
+		reg = <2>;
+		interrupt-parent = <&gpio0>;
+		interrupts = <19 IRQ_TYPE_LEVEL_HIGH>;
+	};
+};