Android Open Source Project (AOSP)

1. Android core overview

   Entry page for the Android platform internals documentation.

2. Android architecture

   Layers from kernel and HAL to framework.

3. Hardware abstraction layer

   HAL interface definitions between the framework and vendor drivers.

4. AIDL for HALs

   AIDL interfaces for HALs and Treble.

5. Android Runtime (ART)

   AOT and JIT compilation and garbage collection.

6. Kernel

   Android kernel requirements and GKI.

7. SELinux for Android

   SELinux domains, policy files and sepolicy for Android.

8. Set up and build AOSP

   Downloading and building the source tree.

9. Performance

   Boot time, memory and power tuning.

10. Permissions

    Permissions and privileged apps.

11. Security overview

    Android platform security model including sandboxing and verified boot.

Each section links to the official page. Titles and summaries by Extra Credit; the docs belong to their authors.