net: phy: Add support for Aeonsemi AS21xxx PHYs

Add support for Aeonsemi AS21xxx 10G C45 PHYs. These PHYs integrate
an IPC to setup some configuration and require special handling to
sync with the parity bit. The parity bit is a way the IPC use to
follow correct order of command sent.

Supported PHYs AS21011JB1, AS21011PB1, AS21010JB1, AS21010PB1,
AS21511JB1, AS21511PB1, AS21510JB1, AS21510PB1, AS21210JB1,
AS21210PB1 that all register with the PHY ID 0x7500 0x7510
before the firmware is loaded.

They all support up to 5 LEDs with various HW mode supported.

While implementing it was found some strange coincidence with using the
same logic for implementing C22 in MMD regs in Broadcom PHYs.

For reference here the AS21xxx PHY name logic:

AS21x1xxB1
    ^ ^^
    | |J: Supports SyncE/PTP
    | |P: No SyncE/PTP support
    | 1: Supports 2nd Serdes
    | 2: Not 2nd Serdes support
    0: 10G, 5G, 2.5G
    5: 5G, 2.5G
    2: 2.5G

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
Link: https://patch.msgid.link/20250517201353.5137-6-ansuelsmth@gmail.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>