quoted

Do you know why the reset times out/fails?

Because there are nothing connected to it.

That should not be an issue. A read should just return 0xffff.  And it
should return 0xffff fast. The timing of the MDIO protocol is fixed. A
read or a write takes a fixed number of cycles, independent of if
there is a device there or not. The bus data line has a pullup, so if
you try to access a missing device, you automatically read 0xffff.

       Andrew