Its very smooth and happens in a structured manner.
You would first be interviewed over phone or Skype within 10-15 days of application. In this you are asked mostly about whats in your CV, in detail.
Following this, if successful, you would be called for a face to face interview again within 10 to 15 days, also based on your convenience. However, if not through from previous step you would receive a detailed email, again in a short span of time.
In the face to face interview, you would first have to talk about yourself, projects, say whatever best describes your capabilities, then there would a 2 to 3 technical questions, based on area of application. Its very warm and friendly, usually with two interviewers, in a small meeting room.
All the best to aspirants. Its a wonderful experience, here at ARM. See you soon!