Hi Usman,

Why don't you call a method from your button and return an action from the method.

In the method, pass a domain in the action which will show you the RFQs related to your record.

    @api.multi
    def open_rfq(self):
        self.ensure_one()
        action = self.env.ref('purchase.purchase_rfq').read()[0]
        action.update({
            'domain': [('ssr_id', '=', self.id)]
        })
        return action

Hope this will work for you.