class Route(models.Model):
    title = models.CharField(20)
    region = models.ForeignKey(Region, on_delete=models.DO_NOTHING)
    dealer_points = models.ManyToManyField(DealerPoint)

class Region(models.Model):
    name = models.CharField(30)

class DealerPoint(models.Model):
    address = models.CharField(30)
    region = models.ForeignKey(Region, on_delete=models.DO_NOTHING, null=True)