net: phy: Add Airoha phy library for shared code

In preparation of Airoha AN8801R PHY support, split out the interface
functions that will be common between the already present air_en8811h
driver and the new one, and put them into a new library named
air_phy_lib.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com>
Link: https://patch.msgid.link/20260526-add-airoha-an8801-support-v5-2-01aea8dee69b@collabora.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/phy/Kconfig

@@ -92,10 +92,16 @@ config AS21XXX_PHY
 
 config AIR_EN8811H_PHY
 	tristate "Airoha EN8811H 2.5 Gigabit PHY"
+	select AIR_NET_PHYLIB
 	select PHY_COMMON_PROPS
 	help
 	  Currently supports the Airoha EN8811H PHY.
 
+config AIR_NET_PHYLIB
+	tristate
+	help
+	  Airoha Ethernet PHY common library
+
 config AMD_PHY
 	tristate "AMD and Altima PHYs"
 	help

drivers/net/phy/Makefile

@@ -30,6 +30,7 @@ obj-y				+= $(sfp-obj-y) $(sfp-obj-m)
 obj-$(CONFIG_ADIN_PHY)		+= adin.o
 obj-$(CONFIG_ADIN1100_PHY)	+= adin1100.o
 obj-$(CONFIG_AIR_EN8811H_PHY)   += air_en8811h.o
+obj-$(CONFIG_AIR_NET_PHYLIB)	+= air_phy_lib.o
 obj-$(CONFIG_AMD_PHY)		+= amd.o
 obj-$(CONFIG_AMCC_QT2025_PHY)	+= qt2025.o
 obj-$(CONFIG_AQUANTIA_PHY)	+= aquantia/

drivers/net/phy/air_en8811h.c

@@ -21,6 +21,8 @@
 #include <linux/wordpart.h>
 #include <linux/unaligned.h>
 
+#include "air_phy_lib.h"
+
 #define EN8811H_PHY_ID		0x03a2a411
 #define AN8811HB_PHY_ID		0xc0ff04a0
 
@@ -40,7 +42,6 @@
 #define   AIR_AUX_CTRL_STATUS_SPEED_1000	0x8
 #define   AIR_AUX_CTRL_STATUS_SPEED_2500	0xc
 
-#define AIR_EXT_PAGE_ACCESS		0x1f
 #define   AIR_PHY_PAGE_STANDARD			0x0000
 #define   AIR_PHY_PAGE_EXTENDED_4		0x0004
 
@@ -244,16 +245,6 @@ static const unsigned long en8811h_led_trig = BIT(TRIGGER_NETDEV_FULL_DUPLEX) |
 					      BIT(TRIGGER_NETDEV_RX)          |
 					      BIT(TRIGGER_NETDEV_TX);
 
-static int air_phy_read_page(struct phy_device *phydev)
-{
-	return __phy_read(phydev, AIR_EXT_PAGE_ACCESS);
-}
-
-static int air_phy_write_page(struct phy_device *phydev, int page)
-{
-	return __phy_write(phydev, AIR_EXT_PAGE_ACCESS, page);
-}
-
 static int __air_buckpbus_reg_write(struct phy_device *phydev,
 				    u32 pbus_address, u32 pbus_data)
 {

drivers/net/phy/air_phy_lib.c

@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Airoha Ethernet PHY common library
+ *
+ * Copyright (C) 2026 Airoha Technology Corp.
+ * Copyright (C) 2026 Collabora Ltd.
+ *                    Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com>
+ */
+
+#include <linux/export.h>
+#include <linux/module.h>
+#include <linux/phy.h>
+
+#include "air_phy_lib.h"
+
+#define AIR_EXT_PAGE_ACCESS		0x1f
+
+int air_phy_read_page(struct phy_device *phydev)
+{
+	return __phy_read(phydev, AIR_EXT_PAGE_ACCESS);
+}
+EXPORT_SYMBOL_GPL(air_phy_read_page);
+
+int air_phy_write_page(struct phy_device *phydev, int page)
+{
+	return __phy_write(phydev, AIR_EXT_PAGE_ACCESS, page);
+}
+EXPORT_SYMBOL_GPL(air_phy_write_page);
+
+MODULE_DESCRIPTION("Airoha PHY Library");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Louis-Alexis Eyraud");

drivers/net/phy/air_phy_lib.h

@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Copyright (C) 2026 Airoha Technology Corp.
+ * Copyright (C) 2026 Collabora Ltd.
+ *                    Louis-Alexis Eyraud <louisalexis.eyraud@collabora.com>
+ */
+
+#ifndef __AIR_PHY_LIB_H
+#define __AIR_PHY_LIB_H
+
+#include <linux/phy.h>
+
+int air_phy_read_page(struct phy_device *phydev);
+int air_phy_write_page(struct phy_device *phydev, int page);
+
+#endif /* __AIR_PHY_LIB_H */