Relevant doc for Android / Linux Development

ARM v7 Reference Manual
ARM v8 Reference Manual

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GCC
DTS wiki
Make Manual
KConfig Manual
Linker Script Manual
GDB Manual
Linux Device Driver

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Repo Manual
Android Brief Manual from Google
Android Build System
Android Building Kernel
Android Porting Tutorial
Android Porting Example

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NanoPC-T3 wiki
NanoPC-T3S5P6818 Datasheet