title: How to filter choices in fields(forms) in Django admin?
body: <p>I have model Tech, with name(Charfield) and firm(ForeignKey to model Firm), because one Tech(for example, smartphone) can have many firms(for example Samsung, apple, etc.)</p>
  
  <p>How can I create filter in admin panel for when I creating model, If I choose 'smartphone' in tech field, it show me in firm field only smartphone firms? Coz if I have more than one value in firm field (for example Apple, Samsung, IBM), it show me all of it. But IBM must show only if in tech field I choose 'computer'. How release it?</p>