Greetings @dmaster,
On initial inspection I don’t see anything immediately wrong. I’m not too familiar with the fixed-link node you are using. But it seems to be a valid node according to the documentation I can find. Other than that it seems like your settings/configurations for fec2 more or less mirror what we have in fec1 so that should be fine. Other than this the only thing to make sure is that the pins in pinctrl_fec2 aren’t being used for other interfaces or subsystems.
Though now that I look at your pinctrl_fec node I believe the syntax with the node isn’t correct. You’re calling a node with the panhandle &pinctrl this only works if there’s an existing node in the device tree somewhere with the panhandle pinctrl. This isn’t what you’re trying to do, you’re trying to define a brand new pinctrl node.
For an example of how to define new pinctrl nodes in an overlay see the solution on this other thread: Device Tree Overlay to enable a GPIO pin on Colibri iMX8 DualX 1GB - #7 by hfranco.tx
Best Regards,
Jeremias