linux串口调试demo,可以支持多种平台，arm,mipsel-linux serial test demo

基于ARM开发板的linux下的串口编程，做好两个API函数，可供应用程序直接调用，设置方便简单，感兴趣的也可以研究函数内部详细设置过程。-ARM-based development board serial programming under linux, do two API functions are available directly calling application, easy to set up, you can also set up a detailed study of