CMake to build project as library modules

Question

I am trying to use CMake to build a project that contains several modules.

project
--modules
  CMakeLists.txt

  --mod1
    CMakeLists.txt
    --src
      --*.cpp
    --include
      --*.h

  --mod2
    CMakeLists.txt
    --src
      --*.cpp
    --include
      --*.h

--applications

This is similar to how openCV is structured. I am trying to write macros similar to what openCV where you simply say add_module(mod1 DEPENDS mod2) and it would go in and recursively install mod1 and all its dependencies. I also want to be able to build specific modules. Unfortunately I am unable to find many CMake examples structured this way. The OpenCV macros are very involved and difficult to distill the basic CMake commands. Any help is appreciated!