hello aplb,
here’s forum discussion thread for your reference, gpio interrupts from user space.
you may also access L4T sources packages from download center for reference,
please refer to below source, by checking cd_gpio for an example to process an interrupt from a GPIO.
thanks
$L4T_Sources/r32.5/Linux_for_Tegra/source/public/kernel/kernel-4.9/drivers/mmc/host/sdhci-tegra.c