For Samsung TVs, the name they use for HDMI CEC is Anynet+. Search for that in the settings. Waking the Apple TV should automatically wake the Samsung TV if this is enabled and working properly, as JBaby said, and that’s how my ATV and Samsung TV work. Don’t think Samsung TVs themselves are actually supported by Siri Shortcuts so it would have to be through the Apple TV.
Open Shortcuts>Click My Shortcuts Tab (bottom left)>Click “+” (top right)>Add Action>Type “Remote” in search field (top)>Click Apple TV Remote (where search results are)>Click Wake Apple TV>Next to the word “Wake” there should be a blue subdued “Apple TV”. Click on that to bring up your list of Apple TV’s from the bottom. Click on the Apple TV you’d like to wake with this Shortcut>Click “Next (top right)>Give your Shortcut a name for Siri to recognize>Done (Top right)