I could give you a theoretical answer that could land you in trouble. But, a practical answer to your question (whether in IIT or any other college in India or US) would be: You don't. I don't think it is a good idea to tell him anything. There are many possible reasons that may cause him to be late, but you are not in a position to ask him to be on time. He is in a superior position to you and you don't have the authority to tell him to be on time.
I don't think any of my Ph.D. adviser's students (in US) would have told my adviser to be on time for the weekly meeting if he were consistently late. He was quite friendly, but I don't think any of his students would have dared to tell that to him.
If I were consistently late for my meetings and any of my students were to ask me to be on time, honestly, I would be a little hurt but I would try to be on time for my future meetings. Professors are also humans and they have certain expectations of their students. You gain very little by asking your professor to be on time, but might lose by doing that.
So, my advice would be to take some reading material or an assignment that you are working on and wait for your professor to show up. Please give the benefit of doubt to your professor. There are some students who are consistently late to the class and the whole class expects the professor to be sympathetic towards them. Let us be sympathetic to the professors as well. They are also humans.
I like to blog about various topics ranging from education in IITs to social issues in India and US. All opinions and views presented here are my own and not of my employer.