See attached patch, heavily based on other commits.

Looks good.

You need to add a Signed-off-by: See

https://www.kernel.org/doc/html/latest/process/submitting-patches.html#sign-your-work-the-developer-s-certificate-of-origin

Patches need to be in the body of the email, not attachments.

You can use scripts/get_maintainers.pl to get a list of people to send
it to. I would use To: for
Maxime Ripard [off-list ref] (maintainer:ARM/Allwinner sunXi SoC support)
Chen-Yu Tsai [off-list ref] (maintainer:ARM/Allwinner sunXi SoC support)
Jernej Skrabec [off-list ref] (reviewer:ARM/Allwinner sunXi SoC support)

and Cc: for the rest.

Note: running `git grep 'phy-mode\s*=\s*"rgmii"' arch` shows that it might
affect other hardware as well.

"rgmii" can be correct. So you need to narrow your search.

I don't know how one is supposed to check
that, but I would guess at least sun50i-a64-nanopi-a64.dts is affected (a
quick internet search shows that it's using a RTL8211E¹)

This seems reasonable. You could provide a second patch for this.

     Andrew