Examples for creating firmware for multiple targets?

[saosebastiao]

I realize there are probably hundreds of ways to do the same thing, but it would be nice to have an example of some best practices for writing code that targets different microcontrollers, using different pinouts, etc., perhaps using the embedded_hal feature (if that makes it easier, not sure). For example, I'm currently targeting a G4 microcontroller, but what if I want to create a different board with an additional sensors and firmware features on an H5 microcontroller, what would be the best way to write my code to ensure I can easily port existing functionality in the new target?