Buildroot is a set of Makefiles and patches that makes it easy to generate a complete embedded Linux system. Buildroot can generate any or all of a cross-compilation toolchain, a root filesystem, a kernel image and a bootloader image. Buildroot is useful mainly for people working with small or embedded systems, using various CPU architectures. It automates the building process of your embedded system and eases the cross-compilation process. The official buildroot site is at buildroot.uclibc.org
The source and documentation found here is specific to the Blackfin processor. If you have any questions about buildroot distribution for the Blackfin processor please ask them here.