[RFC PATCH 9/9] upl: Add initial documentation

[Simon Glass]

Add some placeholder documentation to explain the basic concept. Once the
spec is published, more can be added and this series applied.

Signed-off-by: Simon Glass <sjg at chromium.org>
---

 doc/usage/index.rst |  1 +
 doc/usage/upl.rst   | 27 +++++++++++++++++++++++++++
 2 files changed, 28 insertions(+)
 create mode 100644 doc/usage/upl.rst

diff --git a/doc/usage/index.rst b/doc/usage/index.rst
index ed896dfb3a0..78665fd5759 100644
--- a/doc/usage/index.rst
+++ b/doc/usage/index.rst
@@ -13,6 +13,7 @@ Use U-Boot
    partitions
    cmdline
    semihosting
+   upl
 
 Shell commands
 --------------
diff --git a/doc/usage/upl.rst b/doc/usage/upl.rst
new file mode 100644
index 00000000000..2ae4d4a1178
--- /dev/null
+++ b/doc/usage/upl.rst
@@ -0,0 +1,27 @@
+Universal Payload
+~~~~~~~~~~~~~~~~~
+
+Universal Payload (UPL) is an upcoming Industry Standard for firmware
+components. UPL is designed to improve interoperability within the firmware
+industry, allowing mixing and matching of projects with less friction and fewer
+project-specific implementations. UPL is cross-platform, supporting ARM, x86 and
+RISC-V initially.
+
+UPL is defined in termns of two firmware components:
+
+`Platform Init`
+	Perhaps initial setup of the hardware and jumps to the payload.
+
+`Payload`
+	Selects the OS to boot
+
+In practice UPL can be used to handle any number of handoffs through the
+firmware startup process, with one program acting as platform init and another
+acting as the payload.
+
+UPL provides a standard for three main pieces:
+
+- file format for the payload, which may comprise multiple images to load
+- handoff format for the information the payload needs, such as serial port,
+  memory layout, etc.
+- machine state and register settings at the point of handoff
-- 
2.42.0.rc2.253.gd59a3bf2b4-goog