Add fuzz input maintenance docs to the readme

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,6 +1,3 @@
-If you are adding fuzz seeds, please "merge" the seeds before submitting this
-pull request, then remove the instruction text here.
-
-You can use the libFuzzer option `-merge=1` (recommended with
-`-use_value_profile=1`) or the `--m_dir` option of the fuzz runner:
-https://github.com/bitcoin/bitcoin/blob/master/test/fuzz/test_runner.py
+Please see the
+[README.md](https://github.com/bitcoin-core/qa-assets/blob/main/README.md) for
+instructions on how to contribute new inputs.

README.md

@@ -1,2 +1,40 @@
 # qa-assets
-Bitcoin Core related blobs used for quality assurance
+
+Bitcoin Core related blobs used for quality assurance.
+
+## Fuzz inputs
+
+`qa-assets/fuzz_seed_corpus` contains one input corpus per fuzz target (one
+folder per target named the same as each target).
+
+### Contributing inputs
+
+*For documentation on how to fuzz Bitcoin Core please see
+[fuzzing.md](https://github.com/bitcoin/bitcoin/blob/master/doc/fuzzing.md).*
+
+If you want to contribute fuzz inputs, please "merge" the inputs before
+submitting a pull request. You can use the libFuzzer option `-merge=1`
+(recommended with `-use_value_profile=1`) or the `--m_dir` option of the fuzz
+runner:
+[`test_runner.py`](https://github.com/bitcoin/bitcoin/blob/master/test/fuzz/test_runner.py).
+
+### Pruning inputs 
+
+* Over time fuzz engines reduce inputs (produce a smaller input that yields the
+  same coverage statistics), which causes our copora to accumulate larger
+  non-reduced inputs. 
+* Code changes can lead to inputs losing their coverage.
+
+To avoid corpora bloat, stale inputs and potential CI timeouts, we usually
+prune/minimize our copora around the branch-off point using the
+[`delete_nonreduced_fuzz_inputs.sh`](https://raw.githubusercontent.com/bitcoin-core/bitcoin-maintainer-tools/main/delete_nonreduced_fuzz_inputs.sh)
+script (Recommended to run in a fresh VM, see documentation in the script). The
+script is usually run twice to ensure that the results are "somewhat"
+reproducible (e.g.
+https://github.com/bitcoin-core/qa-assets/pull/119#issuecomment-1518019457).
+
+After pruning the corpora, the coverage should not have dropped at all.
+
+### Pulling inputs from oss-fuzz
+
+Use `download_oss_fuzz_inputs.py` to pull fuzz inputs from oss-fuzz.