[SalesForce] Display spinner in specific component only

I think a better approach to handle that would be as parent/child components:

On the List component include the details/child component:

<c:DetailArticle aura:id="detailArticle" />

Then add an aura:method on the details/child component - instead of the event:

<aura:method name="openArticle" action="{!c.openArticle}" access="PUBLIC"> 
    <aura:attribute name="articleId" type="String" />
</aura:method>

Now handle that method from your details/child component's controller:

openArticle : function(cmp, event) {
    var params = event.getParam('arguments');
    if (params) {
        var atrId = params.articleId;
        console.log("article id: " + atrId);
        // add the article to the details page
    }
}

Now on your parent list component controller, when you want to open the article detail page from your button list controller - fire the apexMethod event like that:

getDetail : function(component, event, helper){

    // 1. get the details component
    var details = component.find("DetailArticle")

    // 2. get the article id
    var articleId = event.target.getAttribute("data-recId");

    // 3. run the child component init (aura:method)
    details.openArticle(articleId);
}

You need to apply position: relative to the component element, in your case uploadCard. This contains the overlay to within the boundaries of your component The following code works as expected (jsfiddle.net) and overlays only your component:

<div aura:id="uploadCard" class="slds-card__header" style="position:relative">
  <div class="slds-form--compound">
    <div>content goes here</div>
    <div class="slds-spinner_container" aura:id="uploadSpinner">
      <div class="slds-spinner slds-spinner--medium" aria-hidden="false" role="alert">
        <div class="slds-spinner__dot-a"></div>
        <div class="slds-spinner__dot-b"></div>
      </div>
    </div>
  </div>
</div>

It will render like this:

Alternatively, you can assign the class .slds-is-relative which has the same effect:

<div aura:id="uploadCard" class="slds-card__header slds-is-relative">...</div>