The way it works is really weird, and completely nonintuitive, but it does work.
You have to set up one smart light automation which turns it after a specific period of time. The following post has a screenshot of every step in that process.
Then you set up a second smart lighting automation that turns the light on with your trigger of the Doorbell.
Those two smart lighting automations together will result in the following: you push the doorbell, the light comes on, then the light turned itself off after the amount of time you specified in the first smart lighting automation.
No question it’s not intuitive, it’s not easy to figure out, but it’s nothing to do with the doorbell-- it’s exactly the same thing if you want the porch light to come on for 15 minutes when your presence is detected arriving home.
If you’re willing to take the extra step of creating a virtual switch and use three smart lighting automations, you can set up a virtual timer separate from the light, which gives you a lot more flexibility to use the same light in other ways.
http://thingsthataresmart.wiki/index.php?title=How_to_create_a_virtual_timer_for_a_light
So the options are there, they just aren’t all there at the same time. 
It takes two automations to set up a turn on and then turn off again.