Thanks for the review.  I want to get your thoughts on the outline of
the generic solution. Is the current approach fine and we can extend it
for all shared MDIO use cases/ or do we see any limitations?
 
a) Figure out if the MDIO bus is shared.  (new binding or reuse existing)
b) If the MDIO bus is shared based on DT property then figure out if the 
MDIO producer platform device is probed. If not, defer MDIO consumer
MDIO bus registration.

I actually think you need to talk to the core device model people and
those who support suspend/resume.

It seems like there should be a way to declare a dependency, probably
a probe time, so the core will just do the right things. I don't see
why MDIO busses should be the first to have this problem, so i expect
there already exists a solution.

	Andrew