[yocto] how to use makefile in bitbake

[Liu]

Hi all,
     I have a project which is built by buildroot,so it uses a set of makefiles to build image.But  I want to use bitbake instead of buildroot to build the project.Now I am faced with some difficulties :
 1) How can I use the variables and rules in makefile ? I know bitbake can not parse files like makefile.
  
 Is there any example like this problem? Can anyone give me some good ideas?
  
    Best wishes,
 ---------------Liu
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