From: Andrew Lunn <andrew@lunn.ch>
Date: Mon, Apr 29, 2019 at 14:10:16

Yes, if all i can do is SGMII, hard coding SGMII is fine. But you
should probably check phy-mode and return an error if it has a value
other than SGMII,

+1 because XPCS supports 1000Base-X but it seems this SoC doesn't.

Thanks,
Jose Miguel Abreu