Add initial support for ethernet controller of the Spacemit K3 SoC.
This ethernet controller is almost a standard Synopsys DesignWare
MAC (version 5.40a). This controller require a syscon device to
configure some basic features, like interface type and internal delay.

Change from v2:
- https://lore.kernel.org/netdev/20260121071315.940130-1-inochiama@gmail.com (local)
patch 1:
1. remove not needed compatible for select
2. drop empty line in "spacemit,apmu" properties
3. add spacemit,apmu properties to required.
patch 3:
1. remove misused phy_fix_phy_mode_for_mac_delays.
2. use local tx clock instead of the clk_tx_i in the dwmac.

Change from v1:
- https://lore.kernel.org/netdev/20260120043609.910302-1-inochiama@gmail.com (local)
patch 1:
1. remove phy clock
patch 3:
1. improve comment and include something special about Spacmit K3 dwmac
2. reorder the included file
3. fix wrong delay macro used in spacemit_dwmac_set_delay.
4. add check for maximum supported delay.
5. use DIV_ROUND_CLOSEST to calculate best delay configuration.
6. use assign for the ctrl register initial value.
7. fix input when calling of_property_read_u32().

Inochi Amaoto (3):
  dt-bindings: net: Add support for Spacemit K3 dwmac
  net: stmmac: platform: Add snps,dwmac-5.40a IP compatible string
  net: stmmac: Add glue layer for Spacemit K3 SoC

 .../devicetree/bindings/net/snps,dwmac.yaml   |   2 +
 .../bindings/net/spacemit,k3-dwmac.yaml       | 103 +++++++++
 drivers/net/ethernet/stmicro/stmmac/Kconfig   |  12 +
 drivers/net/ethernet/stmicro/stmmac/Makefile  |   1 +
 .../ethernet/stmicro/stmmac/dwmac-spacemit.c  | 218 ++++++++++++++++++
 .../ethernet/stmicro/stmmac/stmmac_platform.c |   1 +
 6 files changed, 337 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/net/spacemit,k3-dwmac.yaml
 create mode 100644 drivers/net/ethernet/stmicro/stmmac/dwmac-spacemit.c

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2.52.0