Phone interview, followed by 3 rounds of face-to-face interviews.

Questions on C: (check nuances of C like alignments/pointers) Data Structures: Linked Lists questions Operating Systems: Process interactions/scheduling/race conditions/deadlocks etc. Re-entrant code, interrupts, synchronization

Design round questions: Not be tough, look for hints given by interviewer to build on.

The design round can be difficult. This often happens if the interviewer asks questions in an area where you haven't had experience. However, the interviewer usually cares more about your approach than whether you provide the perfect design.