Improve documentation about driver-only p256-m.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/docs/psa-driver-example-and-guide.md b/docs/psa-driver-example-and-guide.md
index 062b05c..85ad258 100644
--- a/docs/psa-driver-example-and-guide.md
+++ b/docs/psa-driver-example-and-guide.md
@@ -146,7 +146,7 @@
     python3 scripts/config.py set MBEDTLS_PSA_P256M_DRIVER_ENABLED
     make
 
-(You need extra steps if you want to disable the built-in implementation of ECC algorithms, which includes more features than p256-m. Refer to the documentation of `MBEDTLS_PSA_P256M_DRIVER_ENABLED` for more information.)
+(You need extra steps if you want to disable the built-in implementation of ECC algorithms, which includes more features than p256-m. Refer to the documentation of `MBEDTLS_PSA_P256M_DRIVER_ENABLED` and `docs/driver-only-builds.md` for more information.)
 
 The driver prefix for p256-m is `P256`/`p256`.
 The p256-m driver implements the following entry points: `import_key`, `export_public_key`, `generate_key`, `key_agreement`, `sign_hash`, `verify_hash`.