STMicroelectronics SoC DWMAC glue layer controller

This file documents differences between the core properties in
Documentation/devicetree/bindings/net/stmmac.txt
and what is needed on STi platforms to program the stmmac glue logic.

The device node has following properties.

Required properties:
 - compatible	: Can be "st,stih415-dwmac", "st,stih416-dwmac",
   "st,stih407-dwmac", "st,stid127-dwmac".
 - st,syscon : Should be phandle/offset pair. The phandle to the syscon node which
   encompases the glue register, and the offset of the control register.
 - st,gmac_en: this is to enable the gmac into a dedicated sysctl control
   register available on STiH407 SoC.
 - pinctrl-0: pin-control for all the MII mode supported.

Optional properties:
 - resets : phandle pointing to the system reset controller with correct
   reset line index for ethernet reset.
 - st,ext-phyclk: valid only for RMII where PHY can generate 50MHz clock or
   MAC can generate it.
 - st,tx-retime-src: This specifies which clk is wired up to the mac for
   retimeing tx lines. This is totally board dependent and can take one of the
   posssible values from "txclk", "clk_125" or "clkgen".
   If not passed, the internal clock will be used by default.
 - sti-ethclk: this is the phy clock.
 - sti-clkconf: this is an extra sysconfig register, available in new SoCs,
   to program the clk retiming.
 - st,gmac_en: to enable the GMAC, this only is present in some SoCs; e.g.
   STiH407.

Example:

ethernet0: dwmac@9630000 {
	device_type = "network";
	compatible = "st,stih407-dwmac", "snps,dwmac", "snps,dwmac-3.710";
	reg = <0x9630000 0x8000>;
	reg-names = "stmmaceth";

	st,syscon = <&syscfg_sbc_reg 0x80>;
	st,gmac_en;
	resets = <&softreset STIH407_ETH1_SOFTRESET>;
	reset-names = "stmmaceth";

	interrupts = <GIC_SPI 98 IRQ_TYPE_NONE>,
		     <GIC_SPI 99 IRQ_TYPE_NONE>,
		     <GIC_SPI 100 IRQ_TYPE_NONE>;
	interrupt-names = "macirq", "eth_wake_irq", "eth_lpi";

	snps,pbl = <32>;
	snps,mixed-burst;

	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_rgmii1>;

	clock-names = "stmmaceth", "sti-ethclk";
	clocks = <&CLK_S_C0_FLEXGEN CLK_EXT2F_A9>,
		 <&CLK_S_C0_FLEXGEN CLK_ETH_PHY>;
};