https://sourceforge.net/p/tceetree/wiki/Home/
Go to your sources root directory and do:
$find . -name "*.c" > cscope.files
#that will recurse subdirectories and list all C files in cscope.files.
$cscope -b -c -R
#(build the cross reference only, don't compress it, recurse);
$./tceetree -V -i cscope.out
#run tceetree with cscope.out as input (default) to get tceetree.out (DOT language representation of function call tree);
$dot -Tpng -O tceetree.out
#to get a graphical representation of the tree in tceetree.out.png.
There are a lot of options you can specify when invoking dot to customize the graph, for example:
you can change output format e.g. to pdf:
$dot -Tpdf -O tceetree.out
you may modify layout from left to right instead of top to bottom:
$dot -Grankdir=LR -Tpng -O tceetree.out
you may modify graph, nodes and edges font:
$dot -Gfontname=Helvetica -Nfontname=Helvetica -Efontname=Helvetica -Tpng -O tceetree.out
see dot.1.pdf and dotguide.pdf within Graphviz documentation for many other options.