quoted

I think the ideal implementation would be the MAC driver calling some 
phy API to apply the quirk, and then that gets passed on to the phy 
driver. Surely this isn't the first case of a MAC-PHY combination 
needing to go fiddle with some special setting.

I was also hoping to find something like that, but I couldn't really
find it. However, I will try looking in that direction. At least we can
identify the broken MAC via the compatible string of the MAC driver, as
they use two different compatibles: 'fsl,imx8mp-fec' (fine) and
'nxp,imx8mp-dwmac-eqos' (affected by the errata).

Maybe see if you can use phy_register_fixup_for_id().

	Andrew