Add support for MediaTek PHYs found in MT7530 and MT7531 switches.
The initialization procedure is from the vendor driver, but due to lack
of documentation, the function of some register values remains unknown.

Signed-off-by: DENG Qingfang <dqfext@gmail.com>
---
RFC v4 -> PATCH v1:
- No changes.

 drivers/net/phy/Kconfig    |   5 ++
 drivers/net/phy/Makefile   |   1 +
 drivers/net/phy/mediatek.c | 112 +++++++++++++++++++++++++++++++++++++
 3 files changed, 118 insertions(+)
 create mode 100644 drivers/net/phy/mediatek.c

diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
index 288bf405ebdb..9db39fb443e6 100644
--- a/drivers/net/phy/Kconfig
+++ b/drivers/net/phy/Kconfig

@@ -207,6 +207,11 @@ config MARVELL_88X2222_PHY
 	  Support for the Marvell 88X2222 Dual-port Multi-speed Ethernet
 	  Transceiver.
 
+config MEDIATEK_PHY
+	tristate "MediaTek PHYs"
+	help
+	  Supports the MediaTek switch integrated PHYs.
+
 config MICREL_PHY
 	tristate "Micrel PHYs"
 	help

diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
index bcda7ed2455d..ab512cb3592b 100644
--- a/drivers/net/phy/Makefile
+++ b/drivers/net/phy/Makefile

@@ -64,6 +64,7 @@ obj-$(CONFIG_LXT_PHY)		+= lxt.o
 obj-$(CONFIG_MARVELL_10G_PHY)	+= marvell10g.o
 obj-$(CONFIG_MARVELL_PHY)	+= marvell.o
 obj-$(CONFIG_MARVELL_88X2222_PHY)	+= marvell-88x2222.o
+obj-$(CONFIG_MEDIATEK_PHY)	+= mediatek.o
 obj-$(CONFIG_MESON_GXL_PHY)	+= meson-gxl.o
 obj-$(CONFIG_MICREL_KS8995MA)	+= spi_ks8995.o
 obj-$(CONFIG_MICREL_PHY)	+= micrel.o

diff --git a/drivers/net/phy/mediatek.c b/drivers/net/phy/mediatek.c
new file mode 100644
index 000000000000..86e6c466b0e9
--- /dev/null
+++ b/drivers/net/phy/mediatek.c

@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-2.0+
+#include <linux/bitfield.h>
+#include <linux/module.h>
+#include <linux/phy.h>
+
+#define MTK_EXT_PAGE_ACCESS		0x1f
+#define MTK_PHY_PAGE_STANDARD		0x0000
+#define MTK_PHY_PAGE_EXTENDED		0x0001
+#define MTK_PHY_PAGE_EXTENDED_2		0x0002
+#define MTK_PHY_PAGE_EXTENDED_3		0x0003
+#define MTK_PHY_PAGE_EXTENDED_2A30	0x2a30
+#define MTK_PHY_PAGE_EXTENDED_52B5	0x52b5
+
+static int mtk_phy_read_page(struct phy_device *phydev)
+{
+	return __phy_read(phydev, MTK_EXT_PAGE_ACCESS);
+}
+
+static int mtk_phy_write_page(struct phy_device *phydev, int page)
+{
+	return __phy_write(phydev, MTK_EXT_PAGE_ACCESS, page);
+}
+
+static void mtk_phy_config_init(struct phy_device *phydev)
+{
+	/* Disable EEE */
+	phy_write_mmd(phydev, MDIO_MMD_AN, MDIO_AN_EEE_ADV, 0);