dt-bindings: net: ks8995: add bindings documentation for ks8995

Signed-off-by: NHelmut Buchsbaum <helmut.buchsbaum@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/micrel-ks8995.txt

+Micrel KS8995 SPI controlled Ethernet Switch families
+
+Required properties (according to spi-bus.txt):
+- compatible: either "micrel,ks8995", "micrel,ksz8864" or "micrel,ksz8795"
+
+Optional properties:
+- reset-gpios : phandle of gpio that will be used to reset chip during probe
+
+Example:
+
+spi-master {
+	...
+	switch@0 {
+		compatible = "micrel,ksz8795";
+
+		reg = <0>;
+		spi-max-frequency = <50000000>;
+		reset-gpios = <&gpio0 46 GPIO_ACTIVE_LOW>;
+	};
+};