Hi… I have a doubt? Why it is necessary to give name to a logo in a site?
Could you say a bit more about what you mean? The question is not clear.
A Logo [properly called a logotype], by definition, is a symbol that should be recognizable to represent something. Some logos include the company name as part of its design; many do not.
Or are you asking if the “alt” tag on a logo image should include the name?
Your question is quite vague. Apparently, English is not your native language. I suspect you used the word “doubt” when you mean “question”.
Hi, I would like to respond and participate in the discussion 
is important to put the name in the logo, whether it be graphics whether it be part of the alt html tag.
the first because, if you’re not already know, if you have not popularity jet, it may be useful to communicate the name of the company to new customers.
The second reason the name in the alt tag tells the browser so users too, in which site they are, and because web standards require this information to describe images displayed on the site.