microchip: lan865x: add driver support for Microchip's LAN865X MAC-PHY

microchip: lan865x: add driver support for Microchip's LAN865X MAC-PHY

The LAN8650/1 is designed to conform to the OPEN Alliance 10BASE-T1x
MAC-PHY Serial Interface specification, Version 1.1. The IEEE Clause 4
MAC integration provides the low pin count standard SPI interface to any
microcontroller therefore providing Ethernet functionality without
requiring MAC integration within the microcontroller. The LAN8650/1
operates as an SPI client supporting SCLK clock rates up to a maximum of
25 MHz. This SPI interface supports the transfer of both data (Ethernet
frames) and control (register access).

By default, the chunk data payload is 64 bytes in size. The Ethernet
Media Access Controller (MAC) module implements a 10 Mbps half duplex
Ethernet MAC, compatible with the IEEE 802.3 standard. 10BASE-T1S
physical layer transceiver integrated is into the LAN8650/1. The PHY and
MAC are connected via an internal Media Independent Interface (MII).

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Parthiban Veerasooran <Parthiban.Veerasooran@microchip.com>
Link: https://patch.msgid.link/20240909082514.262942-14-Parthiban.Veerasooran@microchip.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>