The SerDes configuration is in the middle of an address space (HSIO) that
is used to configure some parts in the MAC controller driver, that is why
we need to use a syscon so that we can write to the same address space from
different drivers safely using regmap.

Hi Quentin

I assume breaking backwards compatibility is not an issue here, since
there currently is only one board using the DT binding. But it would
be good to give a warning in the cover notes. git bisect will also
break for this one particular board. And since these changes are going
through different trees, it could be quite a big break.

	Andrew