Master A

  _name = 'master.a'

  name = fields.Char('Name')

  partner_id = fields.Many2one('res.partner', string='Customer', domain=[('customer', '=', True)])

  line_ids = fields.One2many('detail.a', 'master_detail_id')

Detail A

  _name = 'detail.a'

  master_detail_id = fields.Many2one('master.a')

  site_name = fields.Char('Site')

Master B

  _name = 'master.b'

  name = fields.Char('Name')

  partner_id = fields.Many2one('res.partner', string='Customer', domain=[('customer', '=', True)])

  line_ids = fields.One2many('detail.b', 'master_detail_id')

Detail B

  _name = 'detail.b'

  master_detail_id = fields.Many2one('master.b')

  site_name = fields.Char('Site')

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when i select Master B partner_id field its detail (Detail B) field (site_name) filter with domain of (Master A) partner_id

how is it possible??