Apple has had a patent[1] for like a decade at this point which involved placing an iPhone into a slot on a laptop so it could be used in a laptop form, with the phone itself serving as the touchpad.

[1]: https://www.tomsguide.com/news/apple-patents-device-that-doc...

Edit to add: the phone itself is intended to be the main processing unit, the “laptop” is just a screen and keyboard.