SAMA5D3 Xplained Board
https://www.linux4sam.org/bin/view/Linux4SAM/Sama5d3XplainedMainPage#Configure_and_Build_the_Linux_ke
How to build Buildroot for AT91
https://www.linux4sam.org/bin/view/Linux4SAM/BuildRootBuild
Documents and Software
https://www.microchip.com/DevelopmentTools/ProductDetails/ATSAMA5D3-XPLD
Microchip's Cortex-A5 SAMA5D3 Development Boards
https://www.digikey.com/eewiki/display/linuxonarm/SAMA5D3
The Buildroot user manual
http://buildroot.uclibc.org/downloads/manual/manual.html#testing-package