I'm not sure I understand the driver changes this is meant to document. Someone else will have to check for consistency with that. Perhaps the reviewer(s) for these changes. Meanwhile, could you upload a full diff next time as already requested in one of these reviews?
s/RGMII,/RGMII;/ (comma splice)
s/in device tree/in the device tree/
While here, you could tweak this to mention the HiFive Unmatched instead. It is a more relevant example.
IMO, device tree properties are beyond the scope of what we would expect in a driver man page. I think it is enough to say the following:
The .Nm driver supports GMII, RGMII, and SGMII PHY connection modes.