See https://groups.google.com/forum/#!topic/pyweb-il/fqaKiay2_-s

organizations_migrations_0001_initial.py

# -*- coding: utf-8 -*-
from __future__ import unicode_literals

from django.db import models, migrations


class Migration(migrations.Migration):

    dependencies = [
    ]

    operations = [
        migrations.CreateModel(
            name='Customer',
            fields=[
                ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
                ('name', models.CharField(max_length=1000)),
            ],
            options={
                'abstract': False,
            },
            bases=(models.Model,),
        ),
        migrations.CreateModel(
            name='Partner',
            fields=[
                ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
                ('name', models.CharField(max_length=1000)),
                ('parent', models.ForeignKey(blank=True, to='organizations.Partner', null=True)),
            ],
            options={
                'abstract': False,
            },
            bases=(models.Model,),
        ),
        migrations.AddField(
            model_name='customer',
            name='parent',
            field=models.ForeignKey(blank=True, to='organizations.Partner', null=True),
            preserve_default=True,
        ),
    ]

organizations_migrations_0002_auto_20141204_1012.py

# -*- coding: utf-8 -*-
from __future__ import unicode_literals

from django.db import migrations
from django.conf import settings


def create_initial_organizations(apps, schema_editor):
    if settings.DEBUG:
        Customer = apps.get_model("organizations", "Customer")
        Partner = apps.get_model("organizations", "Partner")
        p = Partner(name=u"Partner")
        p.save()
        c = Customer.objects.create(name=u"Customer", parent=p)
        c.save()
        assert Customer.objects.exclude(parent=None).count() == 1


class Migration(migrations.Migration):
    dependencies = [
        ('organizations', '0001_initial'),
    ]

    operations = [
        migrations.RunPython(create_initial_organizations,
                             lambda _x, _y: None),
    ]

organizations_models.py

from django.db import models


class Organization(models.Model):
    name = models.CharField(max_length=1000)
    parent = models.ForeignKey("Partner", blank=True, null=True)

    class Meta:
        abstract = True


class Partner(Organization):
    pass


class Customer(Organization):
    pass