[PATCH v4 5/6] docs/about/deprecated: Document RISC-V "pmu-num" deprecation

[Rob Bradford]

This has been replaced by a "pmu-mask" property that provides much more
flexibility.

Signed-off-by: Rob Bradford <rbradford@rivosinc.com>
Acked-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
---
 docs/about/deprecated.rst | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst
index 2febd2d12f..857b5d4fc4 100644
--- a/docs/about/deprecated.rst
+++ b/docs/about/deprecated.rst
@@ -405,6 +405,18 @@ Specifying the iSCSI password in plain text on the command 
line using the
 used instead, to refer to a ``--object secret...`` instance that provides
 a password via a file, or encrypted.
 
+CPU device properties
+'''''''''''''''''''''
+
+``pmu-num=n`` on RISC-V CPUs (since 8.2)
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+In order to support more flexible counter configurations this has been replaced
+by a ``pmu-mask`` property. If set of counters is continuous then the mask can
+be calculated with ``((2 ^ n) - 1) << 3``. The least significant three bits
+must be left clear.
+
+
 Backwards compatibility
 -----------------------
 
-- 
2.41.0