Views 3 Relationship Handler
Are you really sure you need a relationship handler for this?

In general the default relationship handler is already quite flexible because it uses the default join class which is really powerful.

There are some use cases for relationship handlers, for example the relation module, but this module does some vodoo stuff.

So back to the problem. It might be enought if you define 'relationship' with the right field and base field.

PS: There is a big reason why there is no documentation about api=3 because the difference to api=2 isn't big at all.

Here is an example how to define a relationship.

  $data['node_revision']['vid'] = array(
    'relationship' =&gt; array(
      'handler' =&gt; 'views_handler_relationship',
      'base' =&gt; 'node',
      'base field' =&gt; 'nid',
      'title' =&gt; t('Content'),
      'label' =&gt; t('Get the actual content from a content revision.'),
    ),
  );