Translations:Xorg/Guide/25/en
From Gentoo Wiki
For newer AMD/ATI cards (RadeonHD 2000 and up), emerge sys-kernel/linux-firmware (the package includes firmware for radeon and amdgpu drivers). Once one of these packages has been installed, make the Radeon driver a module in the kernel or, optionally, configure the kernel as detailed in the firmware section of the Radeon article or, for newer AMD graphics cards (GCN1.1+), the firmware section of the AMDGPU article.