Improve documentation of `mbedtls_dhm_make_params`
diff --git a/include/mbedtls/dhm.h b/include/mbedtls/dhm.h
index 542592d..9254d95 100644
--- a/include/mbedtls/dhm.h
+++ b/include/mbedtls/dhm.h
@@ -211,9 +211,11 @@
* \param p_rng RNG parameter
*
* \note The destination buffer must be large enough to hold
- * the modulus, the generator, and the public key, each
- * wrapped with a 2-byte length field. It is the responsibility
- * of the caller to ensure that enough space is available.
+ * the reduced binary presentation of the modulus, the generator
+ * and the public key, each wrapped with a 2-byte length field.
+ * It is the responsibility of the caller to ensure that enough
+ * space is available. Refer to \c mbedtls_mpi_size to computing
+ * the byte-size of an MPI.
*
* \note This function assumes that ctx->P and ctx->G
* have already been properly set (for example