4.1. Compilation system requirements

4.2. Get the source code of linux sdk

   4.2.1. Download orangepi-build from github

   4.2.2. Download the cross-compilation toolchain

   4.2.3. orangepi-build complete directory structure description

4.3. Compile u-boot

4.4. Compile the linux kernel

4.5. Compile rootfs

4.6. Compile linux image