Gitlab groups, subgroups and projects

Hi,

How to restrict gitlab project to one group, So that any new user or user from another group cannot be added.
For example two groups are created in gitlab groupA, groupB. When I am the owner of groupA for a project. I should not able to add user of groupB and individual user should also be restricted.
If there is any feature in gitlab for that, can anyone please provide some solution for it