X now uses black magic to autodetect the suitable device drivers and xorg.conf isn’t needed unless you want to specify something or the autodetection fails.
As responded by Chrysantine and palladium, it is autodetected. However, if you want to tweak it to your customized settings (that is what I did because I wanted my touchpad to behave differently), run “Xorg -configure” to save the detected configuration and then, tweak that file.