File: lib/acme/foo-bundle/Resources/config/doctrine/Car.orm.xml

<?xml version="1.0" encoding="UTF-8"?>
<doctrine-mapping xmlns="http://doctrine-project.org/schemas/orm/doctrine-mapping"
                  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                  xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mapping
                  http://doctrine-project.org/schemas/orm/doctrine-mapping.xsd">

    <entity name="Acme\FooBundle\Entity\Car" table="acme_car" repository-class="Acme\FooBundle\Entity\CarRepository">
        <id name="id" type="integer"><generator strategy="AUTO"/></id>

        <many-to-one field="user" target-entity="\Acme\FooBundle\Entity\UserInterface">
            <join-column name="user_id"
                         referenced-column-name="id"
                         on-delete="CASCADE" />
        </many-to-one>

        <field name="brand" column="brand" type="string" length="180" />

        <field name="model" column="model" type="string" length="180" />
    </entity>

</doctrine-mapping>