Has already been done, many times over many years, by both companies and enthusiasts. If you want to look at the latest developments in the space, I'd recommend following the development of postmarketOS and Jolla / SailfishOS.

Ah, thank you!

People already do and it's not very good.

It's the year of the linux smartphone!

The device tree files are the data which configure the Linux kernel how to interface with the hardware...