I want to change the owner of the file(ContentDocument) uploaded to a case to the owner of the case.
trigger ContentDocumentLinkTrigger on ContentDocumentLink (after insert) 
{
       
    List<ContentVersion> versionsToUpdate = new List<ContentVersion>();
    Map<Id,Id> contentDocIdToCaseId = new Map<Id,Id>();
    Map<Id, Case> mpCase = new Map<Id, Case>();
    Map<Id,ContentVersion> contentMap = new Map<Id,ContentVersion>();

    for(ContentDocumentLink cdl : Trigger.new )
    {
        System.debug('UAC cdl ' + cdl );
        if(String.valueOf(cdl.LinkedEntityId).startsWith('500'))
        {
            contentDocIdToCaseId.put(cdl.ContentDocumentId, cdl.LinkedEntityId);
        }
    }

    System.debug('UAC contentDocIdToCaseId ' + contentDocIdToCaseId ); 
    mpCase = new Map<Id, Case>([SELECT Id, OwnerId FROM Case WHERE Id IN: contentDocIdToCaseId.values()]);
    for(ContentVersion cv : [SELECT Id, OwnerId, ContentDocumentId FROM ContentVersion WHERE ContentDocumentId IN :contentDocIdToCaseId.keySet() AND IsLatest = True])
    {
        contentMap.put(cv.ContentDocumentId, cv);
    }

    System.debug('UAC mpCase ' + mpCase );
    System.debug('UAC contentMap ' + contentMap );

    for(ContentDocumentLink cdl : Trigger.new ) 
    {
        String caseId = cdl.LinkedEntityId ;
        if(mpCase.containsKey(caseId) && contentMap.containsKey(cdl.ContentDocumentId) )
        {
            ContentVersion cv = contentMap.get(cdl.ContentDocumentId);
            cv.OwnerId = mpCase.get(caseId).OwnerId ;
            versionsToUpdate.add(cv);
        }
    } 

    if(versionsToUpdate.size() > 0) update versionsToUpdate ;
}