Hello, Yes it is. I just did this about 2 weeks ago. It took me about 4 hours to figure out all the details of how it all works but now I feel pretty proficient at it. And I have thought of other automations as well like "make all the lights blink 5 times when motion is seen"
For me the easiest way to do this is by going to home.google.com and logging in so you can see your cameras. In the left corner of the screen you should see an "automations" button. Click it and you will be brought to a new screen explaining how it works. If you have ever written software then it will be a big help at figuring it out quicker. But to get you thru it you will use the new AI they have included that will write the routine (mostly) for you. Down in the lower right corner where it says "enter a prompt" you type in english what you want to do. In your case type in "When doorbell camera sees motion turn on porch light for 3 minutes". The system will then generate the many lines of text to do this (probably about 15 lines or so). You will copy everything on the right and replace all the text on the left.
However it may not generate the perfect automation. So you use the VALIDATE button and if there are any errors or warnings the will appear next the line numbers in the routine.
One more hint: for what you are doing you will not need to use the "CONDITIONS" section.
Once you think you have it ready for testing you should SAVE it and then on the right side of the screen turn on the ACTIVATE button. Now go out and give it a try.
Good luck. And don't get frustrated. It takes a little persistence to learn the interface.
