title: Django REST Framework: What's really the difference between validate_<fieldname> and validate?
body: <p>I am performing a custom field-level validation in my serializer that requires referencing another field.</p>
  
  <p>Looking at the examples in the <a href="http://django-rest-framework.org/api-guide/serializers.html#validation" rel="noreferrer">Validation documentation</a>, I'm not clear on whether I should use <code>validate_&lt;fieldname&gt;</code> or <code>validate</code>. It looks like both have the <code>attrs</code> dictionary, so from <code>validate_&lt;fieldname&gt;</code> I can just as easily reference another field as from <code>validate</code> (even though the description for <code>validate</code> indicates that you should use it for accessing multiple fields). So why are there both options? In my case, which option is correct to use?</p>