Update FIPS related build instructions.

This also links back to the new location that lists the cert and
security policy.

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/19617)

README-FIPS.md

@@ -1,13 +1,29 @@
 OpenSSL FIPS support
 ====================
 
-This release of OpenSSL includes a cryptographic module that is intended to be
+This release of OpenSSL includes a cryptographic module that can be
 FIPS 140-2 validated. The module is implemented as an OpenSSL provider.
 A provider is essentially a dynamically loadable module which implements
 cryptographic algorithms, see the [README-PROVIDERS](README-PROVIDERS.md) file
 for further details.
 
-The OpenSSL FIPS provider comes as shared library called `fips.so` (on Unix)
+A cryptographic module is only FIPS validated after it has gone through the complex
+FIPS 140 validation process. As this process takes a very long time, it is not
+possible to validate every minor release of OpenSSL.
+If you need a FIPS validated module then you must ONLY generate a FIPS provider
+using OpenSSL versions that have valid FIPS certificates. A FIPS certificate
+contains a link to a Security Policy, and you MUST follow the instructions
+in the Security Policy in order to be FIPS compliant.
+See <https://www.openssl.org/source/> for information related to OpenSSL
+FIPS certificates and Security Policies.
+
+Newer OpenSSL Releases that include security or bug fixes can be used to build
+all other components (such as the core API's, TLS and the default, base and
+legacy providers) without any restrictions, but the FIPS provider must be built
+as specified in the Security Policy (normally with a different version of the
+source code).
+
+The OpenSSL FIPS provider is a shared library called `fips.so` (on Unix), or
 resp. `fips.dll` (on Windows). The FIPS provider does not get built and
 installed automatically. To enable it, you need to configure OpenSSL using
 the `enable-fips` option.
@@ -15,6 +31,9 @@ the `enable-fips` option.
 Installing the FIPS module
 ==========================
 
+The following is only a guide.
+Please read the Security Policy for up to date installation instructions.
+
 If the FIPS provider is enabled, it gets installed automatically during the
 normal installation process. Simply follow the normal procedure (configure,
 make, make test, make install) as described in the [INSTALL](INSTALL.md) file.