Apalis i.MX8QM poweroff

I have an Apalis i.MX8QM SOM on a custom carrier board that is receiving poweroff button press messages from the SCU (message received by sc_pwrkey linux driver, which powers off the system). It looks like this comes from the SNVS_ON_OFF_BUTTON pin on the i.MX8QM, but that doesn’t seem to go to a pin on the SOM. What is the SNVS_ON_OFF_BUTTON connected to on the SOM? Is there some other condition where the SCU will send power off button events?