MDIO verilog RTL代码，SOC可以通过MDIO接口来访问外部PHY等慢速外设-MDIO verilog RTL code

Management Data Input/Output Interfaces, or MDIO, are specified in the IEEE 802.3 standard. Their primary application is to provide a Serial Management Interface (SMI) to transfer management data between an Ethernet Media Access Controller (MAC)