docs/specs: Convert pci-serial.txt to rst

Convert pci-serial.txt to reStructuredText. This includes
some wordsmithing, and the correction of the docs to note
that the Windows inf file includes 2x and 4x support
(as it has done since commit dc9528fdf9f61 in 2014).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-Id: <20230420160334.1048224-3-peter.maydell@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>

1 files changed, 37 insertions, 0 deletions

diff --git a/docs/specs/pci-serial.rst b/docs/specs/pci-serial.rst
new file mode 100644
index 0000000000..8d916a3669
--- /dev/null
+++ b/docs/specs/pci-serial.rst
@@ -0,0 +1,37 @@
+=======================
+QEMU PCI serial devices
+=======================
+
+QEMU implements some PCI serial devices which are simple PCI
+wrappers around one or more 16550 UARTs.
+
+There is one single-port variant and two multiport-variants.  Linux
+guests work out-of-the box with all cards.  There is a Windows inf file
+(``docs/qemupciserial.inf``) to set up the cards in Windows guests.
+
+
+Single-port card
+----------------
+
+Name:
+  ``pci-serial``
+PCI ID:
+  1b36:0002
+PCI Region 0:
+   IO bar, 8 bytes long, with the 16550 UART mapped to it.
+Interrupt:
+   Wired to pin A.
+
+
+Multiport cards
+---------------
+
+Name:
+  ``pci-serial-2x``, ``pci-serial-4x``
+PCI ID:
+  1b36:0003 (``-2x``) and 1b36:0004 (``-4x``)
+PCI Region 0:
+   IO bar, with two or four 16550 UARTs mapped after each other.
+   The first is at offset 0, the second at offset 8, and so on.
+Interrupt:
+   Wired to pin A.