1) To expedite the required reviews, you may want to add CC to the package maintainers for ArmPkg to this commit message and email. I know a lot of people filter based on direct mention vs mailing list.
2) Generally, other packages have a brief description of the lib in the DEC, as well. Example:
https://github.com/tianocore/edk2/blob/d3b0d007a135284981fa750612a47234b83976f9/MdeModulePkg/MdeModulePkg.dec#L55
However, I see that this has not historically been maintained in this package, so I'm not going to make a big deal of it.
Reviewed-by: Bret Barkelew <bret.barkelew@microsoft.com>