Synopsys R D Engineer interview questions

Applied via job portal. After three weeks, Got a call for first telephonic interview. They asked only basics in C, OS and current project. It went for 45 mins. After two weeks, Got a call for second telephonic round. It went for more than one hour and they asked C concepts, current projects, simple C programm and OS concepts. After one week, Got a call for face to face interview. There were four rounds of interview each one was focusing different skills. Overall they checked C, OS and Hardware knowledge.