I have added a new hardware to my platform.
How can I create an SDK to provide some interface for developers?
I don't need the whole Android SDK like Google provides. It's just about my hardware - as Samsung provides gesture SDK, fingerprint SDK etc. So one can use this special SDK when you develop an app for a Samsung phone.
What You're aiming is SDK Add-on which as the name says is addition to to current SDK.
To generate one from the AOSP write this in the command line:
source build/envsetup.sh
lunch sdk-eng
make PRODUCT-add_on_name-sdk_addon
For a robust guide including how to implement the new add-on look here.