Documentation: RISC-V: patch-acceptance: mention patchwork's role

Palmer suggested at some point, not sure if it was in one of the
weekly linux-riscv syncs, or a conversation at FOSDEM, that we
should document the role of the automation running on our patchwork
instance plays in patch acceptance.

Add a short note to the patch-acceptance document to that end.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20230606-rehab-monsoon-12c17bbe08e3@wendy
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Documentation/riscv/patch-acceptance.rst

@@ -16,6 +16,24 @@ tested code over experimental code.  We wish to extend these same
 principles to the RISC-V-related code that will be accepted for
 inclusion in the kernel.
 
+Patchwork
+---------
+
+RISC-V has a patchwork instance, where the status of patches can be checked:
+
+  https://patchwork.kernel.org/project/linux-riscv/list/
+
+If your patch does not appear in the default view, the RISC-V maintainers have
+likely either requested changes, or expect it to be applied to another tree.
+
+Automation runs against this patchwork instance, building/testing patches as
+they arrive. The automation applies patches against the current HEAD of the
+RISC-V `for-next` and `fixes` branches, depending on whether the patch has been
+detected as a fix. Failing those, it will use the RISC-V `master` branch.
+The exact commit to which a series has been applied will be noted on patchwork.
+Patches for which any of the checks fail are unlikely to be applied and in most
+cases will need to be resubmitted.
+
 Submit Checklist Addendum
 -------------------------
 We'll only accept patches for new modules or extensions if the