How to manage Restriction/Control of visibility of Service Requests to HR Helpdesk administrators?

Content (required): Currently a Helpdesk Administrator can view all Service Requests raised in the fusion by the employees. 

We have a requirement where we want to restrict visibility of Service requests to administrators through legal entity (for assigned as well as unassigned service requests). Can any security rule be configured as such to have different administrators on the basis of Legal entity?

Thanks,

Nidhi