If I Google for "latex textcomp documentation", the most relevant hit is the CTAN textcomp page, which says:
Note that the package has been adopted as part of the LATEX distribution; the reference here is to the original package, which is now little used (if at all).
But I cannot seem to find where the official, current, documentation is for the
textcomp package that comes with LaTeX. The same goes for a number of other packages, such as
Does documentation exist for these packages? Or am I going about this wrong?