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+Building Mbed TLS with PSA cryptoprocessor drivers
+==================================================
+
+**This is a specification of work in progress. The implementation is not yet merged into Mbed TLS.**
+
+This document describes how to build Mbed TLS with additional cryptoprocessor drivers that follow the PSA cryptoprocessor driver interface.
+
+The interface is not fully implemented in Mbed TLS yet and is disabled by default. You can enable the experimental work in progress by setting `MBEDTLS_PSA_CRYPTO_DRIVERS` in the compile-time configuration. Please note that the interface may still change: until further notice, we do not guarantee backward compatibility with existing driver code when `MBEDTLS_PSA_CRYPTO_DRIVERS` is enabled.
+
+## Introduction
+
+The PSA cryptography driver interface provides a way to build Mbed TLS with additional code that implements certain cryptographic primitives. This is primarily intended to support platform-specific hardware.
+
+Note that such drivers are only available through the PSA cryptography API (crypto functions beginning with `psa_`, and X.509 and TLS interfaces that reference PSA types).
+
+Concretely speaking, a driver consists of one or more **driver description files** in JSON format and some code to include in the build. The driver code can either be provided in binary form as additional object file to link, or in source form.
+
+## How to build Mbed TLS with drivers
+
+To build Mbed TLS with drivers:
+
+1. Activate `MBEDTLS_PSA_CRYPTO_DRIVERS` in the library configuration.
+
+    ```
+    cd /path/to/mbedtls
+    scripts/config.py set MBEDTLS_PSA_CRYPTO_DRIVERS
+    ```
+
+2. Pass the driver description files through the Make variable `PSA_DRIVERS` when building the library.
+
+    ```
+    cd /path/to/mbedtls
+    make PSA_DRIVERS="/path/to/acme/driver.json /path/to/nadir/driver.json" lib
+    ```
+
+3. Link your application with the implementation of the driver functions.
+
+    ```
+    cd /path/to/application
+    ld myapp.o -L/path/to/acme -lacmedriver -L/path/to/nadir -lnadirdriver -L/path/to/mbedtls -lmbedcrypto
+    ```
+
+<!-- TODO: what if the driver is provided as C source code? -->
+
+<!-- TODO: what about additional include files? -->