Apple Release iOS 11.0.2 (A Second ) Update for iPhone and iPad. See How To Get It

Apple has released the second update to iOS 11 since its release Sept. 19, and according to the release notes, it addresses the following issues:
  • Fixes an issue where crackling sounds may occur during calls for a small number of iPhone 8 and 8 Plus devices
  • Addresses an issue that could cause some photos to become hidden
  • Fixes an issue where attachments in S/MIME encrypted emails would not open
Since there's no mention of performance or batter-related fixes, it's likely that these issues will have to wait for iOS 11.1, which is currently available for beta testers.

To download the update, go Settings > General > Software Update (the preferred way, and is about 300MB) or connect your iPhone to a computer running iTunes and then carry out the update (this is slower and downloads the entire iOS 11.0.2 package, which is several gigabytes, as opposed to just the smaller update). 
Alternatively, if you prefer a fresh installation or just having a marginal amount of control over the update, then you can download the relevant iOS 11.0.2 IPSW file for your device from the links below and then use iTunes to update or do a clean install.
iOS 11.0.2 Download IPSW Direct Links:

Full iOS 11.0.2 release notes, changelog and other changes can be found here.