Add Android Hardware, how?

Question

Android

Good afternoon, colleagues. I have been using Android for a long time as a consumer, but recently I began to pick it from the other side. Having obtained a radxa scarf , I dabbled with external interfaces, but just turning on the lights through gpio became boring, and I decided to connect the missing devices, for example GPS , but I don’t know how to do it =(
there is a set of functions (for example: android.hardware.wifi), that is, any program that needs a wifi card will call a function that, in turn, will perform the appropriate manipulations through the kernel module?
Explain if I understand the device correctly?! and actually interested (if, of course, I understood everything correctly), how to add these very functions and how to tie devices to them?
Thank you all in advance for your interest in my question. Answered plus to karma and liver =)