PetaLinux Tools 2018.2 uses Yocto Rocko 2.4.1 / Doc Links
This post lists the links to the Rock 2.4.1 Yocto documents.
Yocto Project Reference Manual for 2.4.1 at [link]
Yocto Project Mega-Manual for 2.4.1 at [link]
Yocto Project Quick Start for 2.4.1 at [link]
See [link] for how to figure this out.
Reference
The Xilinx + Yocto graphic is an amalgamation of Xilinx and Yocto icons