relation in multiple table in laravel

I have a three table in laravel.I want to laravel relation to get union list for specific district.

Table:bd_unions

id
upazila_id

Table:bd_upazilas

id
district_id
upazila_en

Table:bd_districts

id
district_en

I need solution using laravel relation.I know using in join to get union list of specic district.

via Chebli Mohamed