rx/tx-internal-delay-ps is used to model a direct MAC to MAC fixed link,
using RGMII, where exactly one of them must supply the delay.
Documentation/networking/phy.rst describes plain rgmii as the mode where
the MAC or the PCB adds the delay rather than the PHY.
This is not correct. phy-mode 'rgmii' in DT means the PCB adds the
delay.
If the value is not 'rgmii', then the MAC/PHY pair need to decided on
which adds the delay, and by convention, it is normally the PHY.
Where it gets interesting is MAC to MAC, which you do see in
switches. Using rx/tx-internal-delay-ps makes a lot of sense in this
setting.
The binding itself looks O.K, its just this commit message text which
is wrong.
Andrew