* Microchip ENC28J60

This is a standalone 10 MBit ethernet controller with SPI interface.

For each device connected to a SPI bus, define a child node within
the SPI master node.

Required properties:
- compatible: Should be "microchip,enc28j60"
- reg: Specify the SPI chip select the ENC28J60 is wired to
- interrupt-parent: Specify the phandle of the source interrupt, see interrupt
                    binding documentation for details. Usually this is the GPIO bank
                    the interrupt line is wired to.
- interrupts: Specify the interrupt index within the interrupt controller (referred
              to above in interrupt-parent) and interrupt type. The ENC28J60 natively
              generates falling edge interrupts, however, additional board logic
              might invert the signal.
- pinctrl-names: List of assigned state names, see pinctrl binding documentation.
- pinctrl-0: List of phandles to configure the GPIO pin used as interrupt line,
             see also generic and your platform specific pinctrl binding
             documentation.

Optional properties:
- spi-max-frequency: Maximum frequency of the SPI bus when accessing the ENC28J60.
  According to the ENC28J80 datasheet, the chip allows a maximum of 20 MHz, however,
  board designs may need to limit this value.
- local-mac-address: See ethernet.txt in the same directory.


Example (for NXP i.MX28 with pin control stuff for GPIO irq):

        ssp2: ssp@80014000 {
                compatible = "fsl,imx28-spi";
                pinctrl-names = "default";
                pinctrl-0 = <&spi2_pins_b &spi2_sck_cfg>;
                status = "okay";

                enc28j60: ethernet@0 {
                        compatible = "microchip,enc28j60";
                        pinctrl-names = "default";
                        pinctrl-0 = <&enc28j60_pins>;
                        reg = <0>;
                        interrupt-parent = <&gpio3>;
                        interrupts = <3 IRQ_TYPE_EDGE_FALLING>;
                        spi-max-frequency = <12000000>;
                };
        };

        pinctrl@80018000 {
                enc28j60_pins: enc28j60_pins@0 {
                        reg = <0>;
                        fsl,pinmux-ids = <
                                MX28_PAD_AUART0_RTS__GPIO_3_3    /* Interrupt */
                        >;
                        fsl,drive-strength = <MXS_DRIVE_4mA>;
                        fsl,voltage = <MXS_VOLTAGE_HIGH>;
                        fsl,pull-up = <MXS_PULL_DISABLE>;
                };
        };