Yes, basically you need to google a little about 'how to reset arduino with button' and 'how to simulate push button on raspberry' 
In general, RPi has a lot easier use of GPIO's than mine OrangePi.
You need to initiate selected GPIO PIN as "out", set it's value to 0.
Then (if I remember correct, so google to be sure) connect transistor:
colletor - to GND of RPi
base - to RPI GPIO pin with small resistor (I don't use it but just don't want to fry your RPi)
emiter - to reset button of arduino
Now, every time you set GPIO to '1' - it's the same as holding reset button on Arduino.
So, to reset it, you have to set value of GPIO to 1 for 1-2 seconds and 'release' button, by setting 0.
I use domoticz and script which checks 'last seen' values for 3 sensors which report maximum every minute.
If all of these 3 sensors have last seen time higher than 75 seconds I can be sure that gateway is frozen and then - voila - my script set's GPIO to reset gateway and everything is working as usual.
It already reset gateway twice during 2 days of work. 
And work flawlessly.
