ecp: introduce new ECP_LIGHT symbol

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/include/mbedtls/build_info.h b/include/mbedtls/build_info.h
index 12a8544..8c41350 100644
--- a/include/mbedtls/build_info.h
+++ b/include/mbedtls/build_info.h
@@ -105,6 +105,13 @@
 #define MBEDTLS_MD_LIGHT
 #endif
 
+/* MBEDTLS_ECP_C is now a subset of MBEDTLS_ECP_LIGHT which contains the
+ * arithmetic part. As a consequence if MBEDTLS_ECP_C is required for
+ * some reason, then MBEDTLS_ECP_LIGHT should be enabled as well. */
+#if defined(MBEDTLS_ECP_C)
+#define MBEDTLS_ECP_LIGHT
+#endif
+
 /* If MBEDTLS_PSA_CRYPTO_C is defined, make sure MBEDTLS_PSA_CRYPTO_CLIENT
  * is defined as well to include all PSA code.
  */
diff --git a/include/mbedtls/check_config.h b/include/mbedtls/check_config.h
index 8e1accd..83c55a0 100644
--- a/include/mbedtls/check_config.h
+++ b/include/mbedtls/check_config.h
@@ -454,7 +454,7 @@
 #endif
 
 #if defined(MBEDTLS_PK_C) && \
-    !defined(MBEDTLS_RSA_C) && !defined(MBEDTLS_ECP_C)
+    !defined(MBEDTLS_RSA_C) && !defined(MBEDTLS_ECP_LIGHT)
 #error "MBEDTLS_PK_C defined, but not all prerequisites"
 #endif
 
diff --git a/include/mbedtls/ecp.h b/include/mbedtls/ecp.h
index b6144d9..9a6717d 100644
--- a/include/mbedtls/ecp.h
+++ b/include/mbedtls/ecp.h
@@ -312,7 +312,7 @@
 /**
  * The maximum size of the groups, that is, of \c N and \c P.
  */
-#if !defined(MBEDTLS_ECP_C)
+#if !defined(MBEDTLS_ECP_LIGHT)
 /* Dummy definition to help code that has optional ECP support and
  * defines an MBEDTLS_ECP_MAX_BYTES-sized array unconditionally. */
 #define MBEDTLS_ECP_MAX_BITS 1
@@ -343,9 +343,9 @@
 #define MBEDTLS_ECP_MAX_BITS 192
 #elif defined(MBEDTLS_ECP_DP_SECP192R1_ENABLED)
 #define MBEDTLS_ECP_MAX_BITS 192
-#else
+#else /* !MBEDTLS_ECP_LIGHT */
 #error "Missing definition of MBEDTLS_ECP_MAX_BITS"
-#endif
+#endif /* !MBEDTLS_ECP_LIGHT */
 
 #define MBEDTLS_ECP_MAX_BYTES    ((MBEDTLS_ECP_MAX_BITS + 7) / 8)
 #define MBEDTLS_ECP_MAX_PT_LEN   (2 * MBEDTLS_ECP_MAX_BYTES + 1)