[kmods PATCH v3] linux/igb_uio: add build instructions

[Thomas Monjalon <thomas@monjalon.net>]

From: Anatoly Burakov <anatoly.burakov@intel.com>

Currently, compilation instructions for igb_uio are missing.
Add them, as well as referring users to per-OS subdirectories.

Signed-off-by: Anatoly Burakov <anatoly.burakov@intel.com>
Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>
Reviewed-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
---
v3: improvements suggested one year ago

No need to wait one more year, this patch is directly applied.
---
 README           |  3 +++
 linux/README.rst | 58 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+)
 create mode 100644 linux/README.rst

diff --git a/README b/README
index e71dbba..c514cf0 100644
--- a/README
+++ b/README
@@ -8,3 +8,6 @@ Now the preference is to contribute kernel modules to the upstream project
 if possible, otherwise to host kernel code in dpdk-kmods.git.
 
 The license can be BSD-3-Clause or GPL-2.0.
+
+For specific instructions per OS,
+please refer to the README file in the respective sub-directory.
diff --git a/linux/README.rst b/linux/README.rst
new file mode 100644
index 0000000..6c60a3d
--- /dev/null
+++ b/linux/README.rst
@@ -0,0 +1,58 @@
+Building Out-of-Tree Kernel Drivers for Linux
+=============================================
+
+Prerequisites
+-------------
+
+The system must have relevant Linux kernel headers or source code installed.
+
+
+Build
+-----
+
+To build ``igb_uio`` driver, simply run ``make`` command
+inside the ``igb_uio`` directory:
+
+.. code-block:: console
+
+   cd igb_uio
+   make
+
+If compiling against a specific kernel source directory is required,
+it is possible to specify the kernel source directory
+using the ``KSRC`` variable:
+
+.. code-block:: console
+
+   make KSRC=/path/to/custom/kernel/source
+
+
+Load
+----
+
+.. note::
+
+   These commands are to be run as ``root`` user.
+
+The ``igb_uio`` driver requires the UIO driver to be loaded beforehand.
+If ``uio`` is not built-in:
+
+.. code-block:: console
+
+   modprobe uio
+
+Then the out-of-tree driver may be loaded.
+
+.. code-block:: console
+
+   insmod igb_uio.ko
+
+
+Clean
+-----
+
+To clean the build directory, the following command can be run:
+
+.. code-block:: console
+
+   make clean
-- 
2.39.1