First name change in Indian passport - living in Manchester, UK

We are living in Manchester, UK on Tier - 2 Visa. My son's passport is about to expire in May 2019, so I am planning to renew it. There are couple of my friends who renewed their child passport from Manchester after visiting vfs office at http://www.vfsglobal.com/india/uk/NEW_I ... sport.html

I want to change his First Name (please note that its a major name change & not just spelling change).
Can anyone please help me what are the procedures & documents required to change name in Indian Passport if applying from Manchester, UK.

Please notice that my son's age in 5 years old.

I found a useful information for USA at third party weblink removed, but don't know whether I have to follow these for UK as well.

Please help.

Note that if you make a major change to his name, you have to inform HO and will also have to get a replacement brp card. Ho will want to see official legal documents changing his name.

Thanks for your quick response.
Yes, my visa is also about to expire. So it will be new Passport & new Visa (and hence new brp).

Can you please let me know steps / procedures ?
Is these steps correct ?
Third party weblin removed

I am not sure this will help you.

If you have a birth certificate and aadhar card with a new name would be helpful.
Along with these, you may also need a notarized certificate.

If you do not have above documents, follow the procedure for a name change for this you may need to contact solicitors. After this only you can apply for a new passport.