HOW-TO-DO

*****
  How to add a new directory into workspace and how to compire source in it?
    ** assume you want add a directory named `dir-a`, source path is `SOURCEDIR`;
       STEP 1. create the directory.
       STEP 2. Modify '`SOURCEDIR`/Makefile':
               case for complire normal:
                    SUB-DIRS:=dir-list `dir-a`
               case for complire separate:
                    SEP-DIRS+=dir-list `dir-a`;
       STEP 3. change directory into `dir-a` and touch Makefile.
       STEP 4. write some pre-define values:
               case 1 for module complire:
                    m-objs:=`module.ko`
                    m-deps:=`module-objs-list ...`
                    include $(WORKDIR)/Rule.make
               case 2 for build-in module:
                    y-deps:=`objs-list ...`
                    include $(WORKDIR)/Rule.make
               case 3 for sub-directory complire:
                (.NOTE you can complire some objects in current directory use case 1, 2.)
                    m-objs:=`module.ko`
                    m-deps:=`module-objs-list ...`
                    y-deps:=`objs-list ...`
                    s-deps:=`objs-list ...`
                    sub-dirs:=`dirs-list ...`
                    include $(WORKDIR)/Rule.make
        STEP 5. enjoy your-self.

*****
  How to config some macro?
    ** assume there is a file `.config`, `.exports`. 
    ** you want to export macro named MY-CONFIG.
       add MY-CONFIG=[m|y|s] into .config
       add EXPORTS+=MY-CONFIG into .exports.