Hi Arash,
In main.tex, I have the line "\input{mypreamble}", and in mypreamble.tex, there's a line with "\usepackage{biblatex}". I also have several "\addbibresource{foo.bib}", "\addbibresource{bar.bib}", etc, either in main.tex or in mypreamble.tex . I would want reftex to be aware of the references in foo.bib and bar.bib whenever main.tex is set as TeX-master, i.e. either while editing main.tex directly or while editing some-section.tex, where some-section.tex sets TeX-master to main.tex.
Best,
Philipp