12d0c0bed3f4 ("phy: phy-mtk-tphy: add a new reference clock")
360f43448f49 ("phy: phy-mtk-tphy: remove unused u3phya_ref clock")
657a9edec075 ("phy: phy-mtk-tphy: make the ref clock optional")
b603c500d7a5 ("phy: phy-mtk-tphy: get optional clock by devm_clk_get_optional()")
8833ebf4f853 ("phy: phy-mtk-tphy: add configurable parameters for slew rate calibrate")