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+Properties for an MDIO bus multiplexer controlled by a memory-mapped device
+
+This is a special case of a MDIO bus multiplexer. A memory-mapped device,
+like an FPGA, is used to control which child bus is connected. The mdio-mux
+node must be a child of the memory-mapped device. The driver currently only
+supports devices with eight-bit registers.
+
+Required properties in addition to the generic multiplexer properties:
+
+- compatible : string, must contain "mdio-mux-mmioreg"
+
+- reg : integer, contains the offset of the register that controls the bus
+ multiplexer. The size field in the 'reg' property is the size of
+ register, and must therefore be 1.
+
+- mux-mask : integer, contains an eight-bit mask that specifies which
+ bits in the register control the actual bus multiplexer. The
+ 'reg' property of each child mdio-mux node must be constrained by
+ this mask.
+
+Example:
+
+The FPGA node defines a memory-mapped FPGA with a register space of 0x30 bytes.
+For the "EMI2" MDIO bus, register 9 (BRDCFG1) controls the mux on that bus.
+A bitmask of 0x6 means that bits 1 and 2 (bit 0 is lsb) are the bits on
+BRDCFG1 that control the actual mux.
+
+ /* The FPGA node */
+ fpga: board-control@3,0 {
+ #address-cells = <1>;
+ #size-cells = <1>;
+ compatible = "fsl,p5020ds-fpga", "fsl,fpga-ngpixis";
+ reg = <3 0 0x30>;
+ ranges = <0 3 0 0x30>;
+
+ mdio-mux-emi2 {
+ compatible = "mdio-mux-mmioreg", "mdio-mux";
+ mdio-parent-bus = <&xmdio0>;
+ #address-cells = <1>;
+ #size-cells = <0>;
+ reg = <9 1>; // BRDCFG1
+ mux-mask = <0x6>; // EMI2
+
+ emi2_slot1: mdio@0 { // Slot 1 XAUI (FM2)
+ reg = <0>;
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ phy_xgmii_slot1: ethernet-phy@0 {
+ compatible = "ethernet-phy-ieee802.3-c45";
+ reg = <4>;
+ };
+ };
+
+ emi2_slot2: mdio@2 { // Slot 2 XAUI (FM1)
+ reg = <2>;
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ phy_xgmii_slot2: ethernet-phy@4 {
+ compatible = "ethernet-phy-ieee802.3-c45";
+ reg = <0>;
+ };
+ };
+ };
+ };
+
+ /* The parent MDIO bus. */
+ xmdio0: mdio@f1000 {
+ #address-cells = <1>;
+ #size-cells = <0>;
+ compatible = "fsl,fman-xmdio";
+ reg = <0xf1000 0x1000>;
+ interrupts = <100 1 0 0>;
+ };