MII_INTERNAL_CTRL_STATUS
reg = phy_read(phydev, MII_INTERNAL_CTRL_STATUS);
err = phy_write(phydev, MII_INTERNAL_CTRL_STATUS, val);
val = phy_read(phydev, MII_INTERNAL_CTRL_STATUS);
ret = phy_write(phydev, MII_INTERNAL_CTRL_STATUS, val);