In the Agile Manifesto, you should prefer working software over comprehensive documentation. If you need an SRS document, there is nothing preventing or discouraging it, but you should give it serious consideration before going through the trouble. Just make sure the creating of the documentation is not at the expense of creating working software. It's not a matter of exclusion or maybe even priority (some industries find these documents to be absolutely required) just keep the end result in mind.
You could also see this as possibly modifying the amount of detail in the documentation or maybe don't write the entire document first, but do it as you go along, so you're not having to make constant changes. It would be a shame to not include changes in your project because an overly robust document becomes too difficult to change or worse no one has noticed that it hasn't.
If you following Agile, User Stories are enough. Agile projects will capture requirements in the form of user stories, scenarios, or other user-centric forms. The best approach will be - decide your components and split them into epics. Then, you can add user stories under epics. No need to create additional SRS. If you need to, and if you are using JIRA for Agile, use 'Confluence' with JIRA. You can create SRS in Confluence and later can split into user stories directly from Confluence. Also, you need to keep the document as a living document.