5) The bus must also be declared somewhere as a device, and registered.
As an example for how one driver implemented an mdio bus driver, see
- drivers/net/gianfar_mii.c and arch/ppc/syslib/mpc85xx_devices.c
+ drivers/net/ethernet/freescale/fsl_pq_mdio.c and an associated DTS file
+ for one of the users. (e.g. "git grep fsl,.*-mdio arch/powerpc/boot/dts/")
Connecting to a PHY