Untitled

<body ng-controller="RegisterController as RegisterCtrl">
<form ng-submit="RegisterCtrl.submit(AvatarCtrl)">
    <div class="avatar" ng-controller="AvatarController as AvatarCtrl">
        <input type="file" ng-model="AvatarCtrl.avatar" />
    </div>

    <input type="text" ng-model="RegisterCtrl.credentials.name" />
    <input type="submit" value="Submit" />
</form>
</body>