Hello Friends,
Approach I am planning to follow for below Scenario- 
I have an EPIC (Project 1) at department level.
Same Project 1 has to be worked between different sub-departments on different functionalities (I am considering those as master story for each department like
A. Master user story 1 name = "Project 1 - Master US1 - sub-department 1"
B. Master user story 2 name = "Project 1 - Master US2 - sub-department 2"
C. Master user story 3 name = "Project 1 - Master US 3- sub-department 3"
Then further master user story will be linked to functional sub user stories with the help of "relates to" like
A. Master story 1 name = "Project 1 - Master story 1 - sub-department 1"
A.1 Sub user Story name 1= Sub US functionality 1
A.2 Sub user Story name 2= Sub US functionality 2 etc
and so on for master user story 2 and 3.
Is there any better way to organize it?
Looking forward for your valuable suggestions and feedback 
Thanks in advance.
Cheers!!