Here is a kernel related part of my work which was helps to develop brand
new PHY device.
It is migth be helpful for developers work with PHY-less lan743x
(7431:0011 in my case). It's just a fake virtual PHY which can change speed of
network card processing as a loopback device. Baud rate can be tuned with
ethtool from command line or by means of SIOCSMIIREG ioctl. Duplex mode not
configurable and it's allways DUPLEX_FULL.
It also provides module parameter mii_regs for setting initial values of
IEEE 802.3 Control Register.