How do I add topics if I send out mailings for 2 different companies

How do I add topics if I send out mailings for 2 different companies

I have company A with product related topics
and company B with Brand related topics
How do I differenciate the 2 companies
Does everybody who checks his topics see all topics,  both A & B ?

Example
A : news
A: events
A: technical bulletin
B: product 1
b: product 2