phy_link_change
phydev->phy_link_change(phydev, true);
phydev->phy_link_change(phydev, false);
phydev->phy_link_change = phy_link_change;
phydev->phy_link_change = NULL;
if (phydev->phy_link_change == phy_link_change)
return !!phydev->phy_link_change;
phy->phy_link_change = phylink_phy_change;
void (*phy_link_change)(struct phy_device *phydev, bool up);