[PATCH 17/19] riscv: hwprobe: Document vendor extensions and xtheadvector extension

[Charlie Jenkins]

Document support for vendor extensions using the key
RISCV_HWPROBE_KEY_VENDOR_EXT_0 and xtheadvector extension using the key
RISCV_ISA_VENDOR_EXT_XTHEADVECTOR.

Signed-off-by: Charlie Jenkins <charlie at rivosinc.com>
---
 Documentation/arch/riscv/hwprobe.rst | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
index b2bcc9eed9aa..38e1b0c7c38c 100644
--- a/Documentation/arch/riscv/hwprobe.rst
+++ b/Documentation/arch/riscv/hwprobe.rst
@@ -210,3 +210,15 @@ The following keys are defined:
 
 * :c:macro:`RISCV_HWPROBE_KEY_ZICBOZ_BLOCK_SIZE`: An unsigned int which
   represents the size of the Zicboz block in bytes.
+
+* :c:macro:`RISCV_HWPROBE_KEY_VENDOR_EXT_0`: A bitmask containing the vendor
+  extensions that are compatible with the
+  :c:macro:`RISCV_HWPROBE_BASE_BEHAVIOR_IMA`: base system behavior. A set of
+  CPUs is only compatible with a vendor extension if all CPUs in the set have
+  the same mvendorid and support the extension.
+
+  * T-HEAD
+
+    * :c:macro:`RISCV_ISA_VENDOR_EXT_XTHEADVECTOR`: The xtheadvector vendor
+        extension is supported in the T-Head ISA extensions spec starting from
+	commit a18c801634 ("Add T-Head VECTOR vendor extension. ").

-- 
2.44.0