Recognize new revision file upload in Document Library

There's a major and minor versioned document library. Users may upload file with the same name existing in the document library, so it takes another minor version. Or users may edit the item in the document library by only changing item fields without uploading a file, so it takes another minor version as well.

I need to understand if user operation is a file upload? I use itemupdated event handling method. But I do not know where to control to understand whether it is a file upload or item editing?

Please help,

Thanks