Custom Filter in Views using Drupal 7
You can follow this using below step:


Go to Administration -> Structure -> Views
Edit your existing view or create new new.
Add Filter 'A' and B in your view
Click on "Rearrange" filter icon in Filter section
Click on "Create new filter group" and move filter "A" and "B" in new filter group.
Select Operator as "Or" in new filter group and save the form.