Demonstration of how you can dynamically filter the queryset containing the objects which are allowed to be set on a field.

filter_queryset.py

class FooSerializer(serializers.ModelSerializer):
    # Any subclass of a RelatedField, which would normally have a queryset
    bar = serializers.HyperlinkedRelatedField(
        queryset=Bar.objects.none(), # don't unintentionally expose information
    )
  
    def __init__(self, *args, **kwargs):
        # Make sure that self.fields is populated
        super().__init__(*args, **kwargs)
        
        # Get some extra parameter, usually either from the request or the view
        baz_id = self.context["view"].kwargs["baz_id"]
        
        # Generate the new, filtered queryset based on this extra value
        bar_queryset = Bar.objects.filter(baz=baz_id)
        
        # Update the queryset of objectd accepted by the field
        self.fields["bar"].queryset = bar_queryset