Doxygen: Group subprojects

Question

I want to generate a global documentation which should contain the documentation of the subprojects, but i have trouble to group it by the subproject. The project structure looks like this:

top project a

• pages
  • *.md
• subproject
  • project b
    • doc
    • pages
      • *.md
    • src
  • subproject c
    • doc
    • pages
      • *.md
    • src

If i just let the documentation generate with the standard setup, all of the markdown files are on the same level. Therefore i want to group the documentation by the subproject. I know that if you add \addtogroup [b,c] to all files you can achieve that, but i don't want to adjust all files. In the best case, i would like the write one file in the top project which groups the input files like this source:

@defgroup b
@addtogroup b
@copydoc doc_x
@{
@}

@defgroup c
@addtogroup c
@copydoc doc_x
@{
@}

The problem is, that you can only specify one file and not a directory, if i'm correct. I would have to generate an extra label for the subproject directory to copy all files. I also tried \include and \ref, but i couldn't really make it work.

The other idea i had, was to generate a "meta" documentation for each subproject, which i can then adjust with the \addtogroup parameter. I tried it with including the refman.tex of one subproject, but i didn't really looks like it works in that way. But in the end i just need a pdf, so can switch to whatever works.