    4xx/Axon EMAC ethernet nodes

    The EMAC ethernet controller in IBM and AMCC 4xx chips, and also
    the Axon bridge.  To operate this needs to interact with a this
    special McMAL DMA controller, and sometimes an RGMII or ZMII
    interface.  In addition to the nodes and properties described
    below, the node for the OPB bus on which the EMAC sits must have a
    correct clock-frequency property.

      i) The EMAC node itself

    Required properties:
    - device_type       : "network"

    - compatible        : compatible list, contains 2 entries, first is
			  "ibm,emac-CHIP" where CHIP is the host ASIC (440gx,
			  405gp, Axon) and second is either "ibm,emac" or
			  "ibm,emac4".  For Axon, thus, we have: "ibm,emac-axon",
			  "ibm,emac4"
    - interrupts        : <interrupt mapping for EMAC IRQ and WOL IRQ>
    - interrupt-parent  : optional, if needed for interrupt mapping
    - reg               : <registers mapping>
    - local-mac-address : 6 bytes, MAC address
    - mal-device        : phandle of the associated McMAL node
    - mal-tx-channel    : 1 cell, index of the tx channel on McMAL associated
			  with this EMAC
    - mal-rx-channel    : 1 cell, index of the rx channel on McMAL associated
			  with this EMAC
    - cell-index        : 1 cell, hardware index of the EMAC cell on a given
			  ASIC (typically 0x0 and 0x1 for EMAC0 and EMAC1 on
			  each Axon chip)
    - max-frame-size    : 1 cell, maximum frame size supported in bytes
    - rx-fifo-size      : 1 cell, Rx fifo size in bytes for 10 and 100 Mb/sec
			  operations.
			  For Axon, 2048
    - tx-fifo-size      : 1 cell, Tx fifo size in bytes for 10 and 100 Mb/sec
			  operations.
			  For Axon, 2048.
    - fifo-entry-size   : 1 cell, size of a fifo entry (used to calculate
			  thresholds).
			  For Axon, 0x00000010
    - mal-burst-size    : 1 cell, MAL burst size (used to calculate thresholds)
			  in bytes.
			  For Axon, 0x00000100 (I think ...)
    - phy-mode          : string, mode of operations of the PHY interface.
			  Supported values are: "mii", "rmii", "smii", "rgmii",
			  "tbi", "gmii", rtbi", "sgmii".
			  For Axon on CAB, it is "rgmii"
    - mdio-device       : 1 cell, required iff using shared MDIO registers
			  (440EP).  phandle of the EMAC to use to drive the
			  MDIO lines for the PHY used by this EMAC.
    - zmii-device       : 1 cell, required iff connected to a ZMII.  phandle of
			  the ZMII device node
    - zmii-channel      : 1 cell, required iff connected to a ZMII.  Which ZMII
			  channel or 0xffffffff if ZMII is only used for MDIO.
    - rgmii-device      : 1 cell, required iff connected to an RGMII. phandle
			  of the RGMII device node.
			  For Axon: phandle of plb5/plb4/opb/rgmii
    - rgmii-channel     : 1 cell, required iff connected to an RGMII.  Which
			  RGMII channel is used by this EMAC.
			  Fox Axon: present, whatever value is appropriate for each
			  EMAC, that is the content of the current (bogus) "phy-port"
			  property.

    Optional properties:
    - phy-address       : 1 cell, optional, MDIO address of the PHY. If absent,
			  a search is performed.
    - phy-map           : 1 cell, optional, bitmap of addresses to probe the PHY
			  for, used if phy-address is absent. bit 0x00000001 is
			  MDIO address 0.
			  For Axon it can be absent, though my current driver
			  doesn't handle phy-address yet so for now, keep
			  0x00ffffff in it.
    - rx-fifo-size-gige : 1 cell, Rx fifo size in bytes for 1000 Mb/sec
			  operations (if absent the value is the same as
			  rx-fifo-size).  For Axon, either absent or 2048.
    - tx-fifo-size-gige : 1 cell, Tx fifo size in bytes for 1000 Mb/sec
			  operations (if absent the value is the same as
			  tx-fifo-size). For Axon, either absent or 2048.
    - tah-device        : 1 cell, optional. If connected to a TAH engine for
			  offload, phandle of the TAH device node.
    - tah-channel       : 1 cell, optional. If appropriate, channel used on the
			  TAH engine.

    Example:

	EMAC0: ethernet@40000800 {
		device_type = "network";
		compatible = "ibm,emac-440gp", "ibm,emac";
		interrupt-parent = <&UIC1>;
		interrupts = <1c 4 1d 4>;
		reg = <40000800 70>;
		local-mac-address = [00 04 AC E3 1B 1E];
		mal-device = <&MAL0>;
		mal-tx-channel = <0 1>;
		mal-rx-channel = <0>;
		cell-index = <0>;
		max-frame-size = <5dc>;
		rx-fifo-size = <1000>;
		tx-fifo-size = <800>;
		phy-mode = "rmii";
		phy-map = <00000001>;
		zmii-device = <&ZMII0>;
		zmii-channel = <0>;
	};

      ii) McMAL node

    Required properties:
    - device_type        : "dma-controller"
    - compatible         : compatible list, containing 2 entries, first is
			   "ibm,mcmal-CHIP" where CHIP is the host ASIC (like
			   emac) and the second is either "ibm,mcmal" or
			   "ibm,mcmal2".
			   For Axon, "ibm,mcmal-axon","ibm,mcmal2"
    - interrupts         : <interrupt mapping for the MAL interrupts sources:
                           5 sources: tx_eob, rx_eob, serr, txde, rxde>.
                           For Axon: This is _different_ from the current
			   firmware.  We use the "delayed" interrupts for txeob
			   and rxeob. Thus we end up with mapping those 5 MPIC
			   interrupts, all level positive sensitive: 10, 11, 32,
			   33, 34 (in decimal)
    - dcr-reg            : < DCR registers range >
    - dcr-parent         : if needed for dcr-reg
    - num-tx-chans       : 1 cell, number of Tx channels
    - num-rx-chans       : 1 cell, number of Rx channels

      iii) ZMII node

    Required properties:
    - compatible         : compatible list, containing 2 entries, first is
			   "ibm,zmii-CHIP" where CHIP is the host ASIC (like
			   EMAC) and the second is "ibm,zmii".
			   For Axon, there is no ZMII node.
    - reg                : <registers mapping>

      iv) RGMII node

    Required properties:
    - compatible         : compatible list, containing 2 entries, first is
			   "ibm,rgmii-CHIP" where CHIP is the host ASIC (like
			   EMAC) and the second is "ibm,rgmii".
                           For Axon, "ibm,rgmii-axon","ibm,rgmii"
    - reg                : <registers mapping>
    - revision           : as provided by the RGMII new version register if
			   available.
			   For Axon: 0x0000012a