Experimental features policy

policies/experimental-features.md

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+Experimental Feature Policy
+===========================
+
+A feature in OpenSSL may be designated as an experimental feature.
+
+No stability or compatibility guarantees are offered for experimental features.
+An experimental feature, or any API, protocol or file format which is part of an
+experimental feature, may be changed arbitrarily and in compatibility-breaking
+ways, or removed entirely at any time, including between releases.
+
+An experimental feature is not enabled by default and must be explicitly enabled
+at build time in order to be used. The enable flag to enable an experimental
+feature must have the form `enable-experimental-XXX`. The corresponding `ifdef`
+shall have the form `OPENSSL_NO_EXPERIMENTAL_XXX`.
+
+A prominent warning should be issued by the configure script if any experimental
+feature is enabled, with a link to a webpage where people can learn more about
+experimental features.
+
+Experimental features may have associated documentation. This documentation is
+not built by default unless the corresponding experimental feature is enabled.
+Man pages for experimental features shall feature a prominent warning that the
+man page relates to an experimental feature.
+
+New internal header files for experimental features can be placed in `internal/`
+as usual. New public header files for experimental features should be named
+`<experimental/XXX.h>`. Such headers shall only be copied at install time if the
+experimental feature in question is enabled, and should have their contents
+guarded by `ifdef` wherever feasible.
+
+Experimental features exist to support the release engineering process where the
+use of a feature branch is not feasible or desirable. Feature branches should be
+used instead of experimental features where it is reasonable to do so.
+
+Experimental features are not required to be in a buildable or usable state at
+the time of a release or at the time of the creation of a release branch.
+
+Nothing relating to an experimental feature shall be considered a CVE or handled
+under the security process.
+
+An experimental feature may have an associated feature scope definition
+document, which is a Markdown file under `doc/experimental-features` which
+provides any relevant context about the feature. In particular, it may clarify
+what is and is not part of the experimental feature (and therefore subject to
+change) where this is not automatically implied via the use of build-time flags,
+`ifdefs`, etc. This document is authoritative for the purposes of what
+constitutes an experimental feature, subject to this policy.
+
+Merging a PR which creates a new experimental feature requires OTC discussion
+and approval. Non-trivial changes to an existing feature scope definition
+document may be subject to OTC review if needed via the standard OTC hold
+process.