Update documentation for MBEDTLS_ENTROPY_NV_SEED
diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
index fcc4a80..86d8aa4 100644
--- a/include/mbedtls/config.h
+++ b/include/mbedtls/config.h
@@ -811,11 +811,20 @@
*
* Requires: MBEDTLS_ENTROPY_C, MBEDTLS_PLATFORM_C
*
- * Note: If you use the default implementation functions that read a seedfile
+ * \note The read/write functions that are used by the entropy source are
+ * determined in the platform layer, and can be modified at runtime and/or
+ * compile-time depending on the flags (MBEDTLS_PLATFORM_NV_SEED_*) used.
+ *
+ * \note If you use the default implementation functions that read a seedfile
* with regular fopen(), please make sure you make a seedfile with the
* proper name (defined in MBEDTLS_PLATFORM_STD_NV_SEED_FILE) and at
* least MBEDTLS_ENTROPY_BLOCK_SIZE bytes in size that can be read from
- * and written to or you will get an entropy source error!
+ * and written to or you will get an entropy source error! The default
+ * implementation will only use the first MBEDTLS_ENTROPY_BLOCK_SIZE
+ * bytes from the file.
+ *
+ * \note The entropy collector will write to the seed file before entropy is
+ * given to an external source, to update it.
*/
//#define MBEDTLS_ENTROPY_NV_SEED