dt-bindings: net: imx-dwmac: Add NXP imx8 DWMAC glue layer

Add description for NXP imx8 families like imx8mp/imx8dxl
that integrate the Synopsys gmac IP version 5.10a.
Signed-off-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/imx-dwmac.txt

+IMX8 glue layer controller, NXP imx8 families support Synopsys MAC 5.10a IP.
+
+This file documents platform glue layer for IMX.
+Please see stmmac.txt for the other unchanged properties.
+
+The device node has following properties.
+
+Required properties:
+- compatible:  Should be "nxp,imx8mp-dwmac-eqos" to select glue layer
+	       and "snps,dwmac-5.10a" to select IP version.
+- clocks: Must contain a phandle for each entry in clock-names.
+- clock-names: Should be "stmmaceth" for the host clock.
+	       Should be "pclk" for the MAC apb clock.
+	       Should be "ptp_ref" for the MAC timer clock.
+	       Should be "tx" for the MAC RGMII TX clock:
+	       Should be "mem" for EQOS MEM clock.
+		- "mem" clock is required for imx8dxl platform.
+		- "mem" clock is not required for imx8mp platform.
+- interrupt-names: Should contain a list of interrupt names corresponding to
+		   the interrupts in the interrupts property, if available.
+		   Should be "macirq" for the main MAC IRQ
+		   Should be "eth_wake_irq" for the IT which wake up system
+- intf_mode: Should be phandle/offset pair. The phandle to the syscon node which
+	     encompases the GPR register, and the offset of the GPR register.
+		- required for imx8mp platform.
+		- is optional for imx8dxl platform.
+
+Optional properties:
+- intf_mode: is optional for imx8dxl platform.
+- snps,rmii_refclk_ext: to select RMII reference clock from external.
+
+Example:
+	eqos: ethernet@30bf0000 {
+		compatible = "nxp,imx8mp-dwmac-eqos", "snps,dwmac-5.10a";
+		reg = <0x30bf0000 0x10000>;
+		interrupts = <GIC_SPI 134 IRQ_TYPE_LEVEL_HIGH>,
+			     <GIC_SPI 135 IRQ_TYPE_LEVEL_HIGH>;
+		interrupt-names = "eth_wake_irq", "macirq";
+		clocks = <&clk IMX8MP_CLK_ENET_QOS_ROOT>,
+			 <&clk IMX8MP_CLK_QOS_ENET_ROOT>,
+			 <&clk IMX8MP_CLK_ENET_QOS_TIMER>,
+			 <&clk IMX8MP_CLK_ENET_QOS>;
+		clock-names = "stmmaceth", "pclk", "ptp_ref", "tx";
+		assigned-clocks = <&clk IMX8MP_CLK_ENET_AXI>,
+				  <&clk IMX8MP_CLK_ENET_QOS_TIMER>,
+				  <&clk IMX8MP_CLK_ENET_QOS>;
+		assigned-clock-parents = <&clk IMX8MP_SYS_PLL1_266M>,
+					 <&clk IMX8MP_SYS_PLL2_100M>,
+					 <&clk IMX8MP_SYS_PLL2_125M>;
+		assigned-clock-rates = <0>, <100000000>, <125000000>;
+		nvmem-cells = <&eth_mac0>;
+		nvmem-cell-names = "mac-address";
+		nvmem_macaddr_swap;
+		intf_mode = <&gpr 0x4>;
+		status = "disabled";
+	};