According to Google Known Sites section of knowledge Graph, if you add a markup you will get your company showing in SERP Knowledge Graph.
Well, can someone please elaborate what is consider as "Known Sites"? is it someone who verified his/her site with a webmaster? or a site that holds the most authority?
Known sites—A known site is the official website for an entity as shown in Knowledge Graph cards. If you add markup to a known site, that data is treated as authoritative and used for Knowledge Graph cards where it is not already determined by data you put into Google My Business. This includes your official logo and social profile links. However, if you enter contact information through Google My Business, that data source is treated as authoritative. We recommend you keep the data sources in sync if you use both types. Read the guide Enhance Your Site's Attributes