Merge branch 'mt7988-support'

Daniel Golle says:

====================
net: dsa: add support for MT7988

The MediaTek MT7988 SoC comes with a built-in switch very similar to
previous MT7530 and MT7531. However, the switch address space is mapped
into the SoCs memory space rather than being connected via MDIO.
Using MMIO simplifies register access and also removes the need for a bus
lock, and for that reason also makes interrupt handling more light-weight.

Note that this is different from previous SoCs like MT7621 and MT7623N
which also came with an integrated MT7530-like switch which yet had to be
accessed via MDIO.

Split-off the part of the driver registering an MDIO driver, then add
another module acting as MMIO/platform driver.

The whole series has been tested on various MediaTek boards:
 * MT7623A + MT7530 (BPi-R2)
 * MT7986A + MT7531 (BPi-R3)
 * MT7988A reference board

Changes since v1:
 * use 'internal' PHY mode where appropriate
 * use regmap_update_bits in mt7530_rmw
 * improve dt-bindings

Changes since RFC v3:
 * WARN_ON_ONCE if register read fails
 * move probing of the reset GPIO and reset controller link out of
   common  probe function, as they are not actually common

Changes since RFC v2:
 * split into many small commits to ease review
 * introduce helper functions to reduce code duplication
 * use helpers for locking to make lock-skipping easier and less ugly
   to implement.
 * add dt-bindings for mediatek,mt7988-switch

Changes since initial RFC:
 * use regmap for register access and move register access to bus-
   specific driver
 * move initialization of MT7531 SGMII PCS to MDIO driver
====================

Signed-off-by: David S. Miller <davem@davemloft.net>