Update docs.

Author: filmor

docs/kernels.rst

@@ -132,6 +132,13 @@ JSON serialised dictionary containing the following keys and values:
   is found, a kernel with a matching `language` will be used.
   This allows a notebook written on any Python or Julia kernel to be properly associated
   with the user's Python or Julia kernel, even if they aren't listed under the same name as the author's.
+- **interrupt_mode** (optional): May be either ``signal`` or ``message`` and
+  specifies how a client is supposed to interrupt cell execution on this kernel,
+  either by sending an interrupt ``signal`` via the operating system's
+  signalling facilities (e.g. `SIGTERM` on POSIX systems), or by sending an
+  ``interrupt_request`` message on the control channel (see
+  :ref:`msging_interrupt`). If this is not specified
+  the client will default to ``signal`` mode.
 - **env** (optional): A dictionary of environment variables to set for the kernel.
   These will be added to the current environment variables before the kernel is
   started.

docs/messaging.rst

@@ -959,6 +959,27 @@ Message type: ``shutdown_reply``::
    socket, they simply send a forceful process termination signal, since a dead
    process is unlikely to respond in any useful way to messages.
 
+.. _msging_interrupt:
+
+Kernel interrupt
+----------------
+
+In case a kernel can not catch operating system interrupt signals (e.g. the used
+runtime handles signals and does not allow a user program to define a callback),
+a kernel can choose to be notified using a message instead. For this to work,
+the kernels kernelspec must set `interrupt_mode` to ``message``. An interruption
+will then result in the following message on the `control` channel:
+
+Message type: ``interrupt_request``::
+
+    content = {}
+
+Message type: ``interrupt_reply``::
+
+    content = {}
+
+.. versionadded:: 5.3
+
 
 Messages on the IOPub (PUB/SUB) channel
 =======================================