net: phy: add driver for MaxLinear MxL86110 PHY

Add support for the MaxLinear MxL86110 Gigabit Ethernet PHY, a low-power,
cost-optimized transceiver supporting 10/100/1000 Mbps over twisted-pair
copper, compliant with IEEE 802.3.

The driver implements basic features such as:
- Device initialization
- RGMII interface timing configuration
- Wake-on-LAN support
- LED initialization and control via /sys/class/leds

This driver has been tested on multiple Variscite boards, including:
- VAR-SOM-MX93 (i.MX93)
- VAR-SOM-MX8M-PLUS (i.MX8MP)

Example boot log showing driver probe:
[    7.692101] imx-dwmac 428a0000.ethernet eth0:
	PHY [stmmac-0:00] driver [MXL86110 Gigabit Ethernet] (irq=POLL)

Signed-off-by: Stefano Radaelli <[email protected]>
Reviewed-by: Andrew Lunn <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>

Author: StefanoRadaelliGit

MAINTAINERS

@@ -14675,6 +14675,7 @@ MAXLINEAR ETHERNET PHY DRIVER
 M:	Xu Liang <[email protected]>
 L:	[email protected]
 S:	Supported
+F:	drivers/net/phy/mxl-86110.c
 F:	drivers/net/phy/mxl-gpy.c
 
 MCAN MMIO DEVICE DRIVER

drivers/net/phy/Kconfig

@@ -275,6 +275,18 @@ config MAXLINEAR_GPHY
 	  Support for the Maxlinear GPY115, GPY211, GPY212, GPY215,
 	  GPY241, GPY245 PHYs.
 
+config MAXLINEAR_86110_PHY
+	tristate "MaxLinear MXL86110 PHY support"
+	help
+	 Support for the MaxLinear MXL86110 Gigabit Ethernet
+	 Physical Layer transceiver.
+	 The MXL86110 is commonly used in networking equipment such as
+	 routers, switches, and embedded systems, providing the
+	 physical interface for 10/100/1000 Mbps Ethernet connections
+	 over copper media.
+	 If you are using a board with the MXL86110 PHY connected to your
+	 Ethernet MAC, you should enable this option.
+
 source "drivers/net/phy/mediatek/Kconfig"
 
 config MICREL_PHY

drivers/net/phy/Makefile

@@ -68,6 +68,7 @@ obj-$(CONFIG_MARVELL_PHY)	+= marvell.o
 obj-$(CONFIG_MARVELL_88Q2XXX_PHY)	+= marvell-88q2xxx.o
 obj-$(CONFIG_MARVELL_88X2222_PHY)	+= marvell-88x2222.o
 obj-$(CONFIG_MAXLINEAR_GPHY)	+= mxl-gpy.o
+obj-$(CONFIG_MAXLINEAR_86110_PHY)	+= mxl-86110.o
 obj-y				+= mediatek/
 obj-$(CONFIG_MESON_GXL_PHY)	+= meson-gxl.o
 obj-$(CONFIG_MICREL_KS8995MA)	+= spi_ks8995.o