dt-bindings: ethernet: eswin: add EIC7700 eth1 RX clock inversion variant

The EIC7700 SoC integrates two GMAC instances. The eth1 MAC exhibits
different RX clock sampling characteristics due to silicon-inherent
timing behavior.

The eth1 MAC has a fixed, non-configurable RX clock-to-data skew at the
MAC input in the order of 4-5 ns. This cannot be compensated solely by
the standard MAC internal delay configuration and PHY delay, and RX clock
inversion is required at 1000Mbps for correct sampling.

The eth1 TX path also includes a fixed silicon-inherent delay of
approximately 2 ns. This delay is always present and cannot be disabled.
It is therefore part of the effective transmit timing observed on the
wire.

For the eth1 variant, the valid tx-internal-delay-ps values include
this fixed delay component. Consequently, the effective range becomes
2000-4540 ps (approximately 2000 ps fixed delay plus 0-2540 ps
programmable delay).

Introduce a dedicated compatible string
"eswin,eic7700-qos-eth-clk-inversion" to represent the eth1 variant,
allowing the driver to apply RX clock inversion only when required by
hardware variant selection.

This keeps SoC-level differentiation without exposing silicon-fixed skew
as configurable device tree parameters.

To reflect this, model the TX internal delay as a base 0-4540 ps range,
and constrain valid values per compatible using conditional schema rules.

Update the binding schema as follows:

  - Define tx-internal-delay-ps as a base range: 0-4540 ps
  - Add compatible-specific constraints using if/then rules:
    * eswin,eic7700-qos-eth:
        max 2540 ps
    * eswin,eic7700-qos-eth-clk-inversion:
        minimum 2000 ps (effective range 2000-4540 ps)

No functional change for existing "eswin,eic7700-qos-eth" users.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Zhi Li <lizhi2@eswincomputing.com>
Link: https://patch.msgid.link/20260707064159.1299-1-lizhi2@eswincomputing.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

0 files changed, 0 insertions, 0 deletions