GPIO interrupt on QEMU

[Swedha R]

Hi team, 
I have arm64 up and  running in Qemu, And I built kernel image, rootfs everything via buildroot open source I cloned from git.
And I customized via make - menuconfig like enabling gpio support, libgpiod module and in device drivers gpio chip named pl061 .
After that, I able to see gpiochip in the /dev directory inside arm running in qemu.
I want to know , how to trigger the gpio line ( that is function for poweroff) and it have to cach and service it in this case. 
The gpiochip has 7 lines in it. How to find which line is a poweroff key , the qemu-virt board has )

This is the qemu-command we used,
qemu-system-aarch64 -M virt -cpu cortex-a53 -nographic -smp 1 -kernel Image -append "rootwait root=/dev/vda console=ttyAMA0" -netdev user,id=eth0 -device virtio-net-device,netdev=eth0 -drive file=rootfs.ext4,if=none,format=raw,id=hd0 -device virtio-blk-device,drive=hd0

Will you please help on it.