The mdio driver interface is generally useful for devices that require
MDIO without the full MII bus interface. This lifts the driver/interface
out of etherswitch(4), and adds a mdio(4) man page.
Submitted by: Landon Fuller <landon@landonf.org>
Differential Revision: https://reviews.freebsd.org/D4606
This is just the chip initialisation code (for now.)
It's not linked into the main build as it requires a bunch of other code
to be tidied up and committed. But it indeed does function as advertised.
Tested:
* AR9344 SoC
