Good fucking luck
Service manuals often aren’t even made anymore let alone wiring diagrams. This is a bigger discussion of things being made to be repairable. It’s one thing if you’re discussing a car (which are increasingly being built like hostile tech, thanks tesla), but your phone/console/laptop/appliance/etc?
Best case scenario it’s made with a few sub assemblies that are designed to be swapped out instead of fixing them. why diagnose the 1 cent capacitor that’s shorting on your phone motherboard and swap it out? That would create skilled labor, save your data, create opportunities for local small businesses, and prevent e waste. Instead let’s just swap the motherboard, or more likely just junk the phone altogether and make it a parts phone so it can be used for someone who needs a new lcd/battery/casing down the line. As a result apple will buy it off of you for $100 (only if you buy a new phone too though, store credit) as a result even though you paid 800 2 years ago and the remaining parts are worth $400 second hand easily
That’s why even when you can get these docs they’re largely worthless. Apple shares their support docs with their self repair program (though you need a current model serial number to access, not freely available). But it’s what’s described above. If you want to change the lcd? Helpful. If you want to fix a boot loop and persevere your flash? Go fuck yourself unless you have backups