FWIW, the patch in $subject does make the splat go away for me.
(I have the PHY driver built as built-in).

The patch in $subject does "Add a list of registered drivers and check
if one is already available before resorting to call request_module();
in this way, if the PHY driver is already there, the MDIO bus can perform
the async probe."

Lets take a step backwards.

How in general should module loading work with async probe? Lets
understand that first.

Then we can think about what is special about PHYs, and how we can fit
into the existing framework.

	Andrew