Custom directory structure

[no]

Hi,

I'm new to automake/autoconf. I have to compile under linux several "portable" 
projects having their own directory structure that does not match the default 
automake/autoconf one. The dir structure 
looks like this:

ProjectName
      |__CommonSrc : src common to all platforms
      |__PlatformName : repository for everything concerning a specific platform
                |__PlateformSrc : platform specific src
                |__Makefile : makefile for the specific plaform

So my sources are not in the same directory as the makefile. They are in 
several directories which are above the one where the makefile is located. This 
structure is a given, I cannot change it, and I 
can't put makefiles inside source directories. I didn't manage to configure 
automake/autoconf to make it generate makefiles for such a structure. Is there 
any way to do that? Any hint?

Thanks for any help,

Olivier.