net: dsa: LAN9303: add I2C managed mode support

In this mode the switch device and the internal phys will be managed via
I2C interface. The MDIO interface is still supported, but for the
(emulated) CPU port only.

Signed-off-by: Juergen Borleis <jbe@pengutronix.de>
CC: devicetree@vger.kernel.org
CC: robh+dt@kernel.org
CC: mark.rutland@arm.com
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/dsa/lan9303.txt

@@ -0,0 +1,62 @@
+SMSC/MicroChip LAN9303 three port ethernet switch
+-------------------------------------------------
+
+Required properties:
+
+- compatible: should be "smsc,lan9303-i2c"
+
+Optional properties:
+
+- reset-gpios: GPIO to be used to reset the whole device
+- reset-duration: reset duration in milliseconds, defaults to 200 ms
+
+Subnodes:
+
+The integrated switch subnode should be specified according to the binding
+described in dsa/dsa.txt. The CPU port of this switch is always port 0.
+
+Note: always use 'reg = <0/1/2>;' for the three DSA ports, even if the device is
+configured to use 1/2/3 instead. This hardware configuration will be
+auto-detected and mapped accordingly.
+
+Example:
+
+I2C managed mode:
+
+	master: masterdevice@X {
+		status = "okay";
+
+		fixed-link { /* RMII fixed link to LAN9303 */
+			speed = <100>;
+			full-duplex;
+		};
+	};
+
+	switch: switch@a {
+		compatible = "smsc,lan9303-i2c";
+		reg = <0xa>;
+		status = "okay";
+		reset-gpios = <&gpio7 6 GPIO_ACTIVE_LOW>;
+		reset-duration = <200>;
+
+		ports {
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			port@0 { /* RMII fixed link to master */
+				reg = <0>;
+				label = "cpu";
+				ethernet = <&master>;
+			};
+
+			port@1 { /* external port 1 */
+				reg = <1>;
+				label = "lan1;
+			};
+
+			port@2 { /* external port 2 */
+				reg = <2>;
+				label = "lan2";
+			};
+		};
+	};