Open question for ECDSA signature that can be resolved during implementation

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/docs/architecture/psa-migration/psa-legacy-bridges.md b/docs/architecture/psa-migration/psa-legacy-bridges.md
index 3039968..fb00705 100644
--- a/docs/architecture/psa-migration/psa-legacy-bridges.md
+++ b/docs/architecture/psa-migration/psa-legacy-bridges.md
@@ -339,3 +339,5 @@
 
 * These functions convert between the signature format used by `mbedtls_pk_{sign,verify}{,_ext}` and the signature format used by `psa_{sign,verify}_{hash,message}`.
 * The input and output buffers can overlap.
+
+[OPEN] Should these functions rely on the ASN.1 module? To be decided when implementing.