I think 5th has its issues, but in my opinion the Matrix rules are one of its strengths. Everything is hackable, and 5th edition has come the closest Shadowrun has ever been to getting rid of the "Decker's turn to do his thing for a couple hours" aspect of game play.
The post before mine mentioned the ambiguity about hacking traffic lights as a negative. I see that ambiguity instead as a positive. It's only a small number of variables that a GM has to invent, and they're all binary in nature.
1) Is the device wireless? It might be hard wired, or it might be wireless throwback... but generally this first variable is "Yes, everything's wireless unless there's a solid reason for it not to be".
2) Is the device slaved in a PAN or WAN? If no, Device Ratings are loose but easy enough to interpret. Civilian grade electronics? Device Rating 1 or 2. If not something cheap/expendable, it's probably 2. In the case of traffic lights, the answer as to whether they're slaved to a Host is dependent upon whether you want the traffic light to be hard to hack or not. Best of all, you get to decide without forfeiting your prerogative to decide the other way on the next traffic light!
3) Is the device inside a Host? If yes, that host must be penetrated because you can't even see icons inside a host unless you're also inside that host. No ability to target=no targeting with hacking actions. Note that this variable is independent of variable 2. Saying yes to this is basically just telling the hacker that it's not an easy hack. (or: that you're going to need a Data Tap) A traffic light can be "inside" a host without being slaved by that host.
I like this edition's matrix rules because of its open-ended, infinite possibilities.
Player asks: Can I hack the guy's sneakers and make him trip? Variable 1) No reason to be hardwired to anything, nor is there any reason most people turn wireless off on things, so sure. Yes to 1). Variable 2) his shoes could be part of a PAN, maybe. Even if you say yes, all it means is you need to figure out what DR his commlink is. Variable 3) Clearly a no. 3 fairly quick and easy answers, so all you really need to do is figure out how to mechanically represent what actually is imposed upon the target if the hacker is successful and the shoes suddenly self-unbuckle or loosen.
Player asks: Can I hack the guy's soup he's slurping? Variable 1) again, unless there's a perfectly good reason to say no, you should be saying yes. Nanopaste broadcasting simsense is perfectly plausible, so sure, why not, it's possible to make his soup smell like poopy diapers so long as he's got a DNI (or oflactory booster cyberware). 2) Surely a no. 3) again, surely a no. Go wild, decker!