dt-bindings: riscv: add Zfh[min] ISA extensions description

Add description of Zfh[min] ISA extensions[1].

Link: https://drive.google.com/file/d/1z3tQQLm5ALsAD77PM0l0CHnapxWCeVzP/view [1]
Signed-off-by: Clément Léger <cleger@rivosinc.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20231114141256.126749-12-cleger@rivosinc.comSigned-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Documentation/devicetree/bindings/riscv/extensions.yaml

@@ -214,6 +214,19 @@ properties:
             instructions as ratified at commit 6d33919 ("Merge pull request #158
             from hirooih/clmul-fix-loop-end-condition") of riscv-bitmanip.
 
+        - const: zfh
+          description:
+            The standard Zfh extension for 16-bit half-precision binary
+            floating-point instructions, as ratified in commit 64074bc ("Update
+            version numbers for Zfh/Zfinx") of riscv-isa-manual.
+
+        - const: zfhmin
+          description:
+            The standard Zfhmin extension which provides minimal support for
+            16-bit half-precision binary floating-point instructions, as ratified
+            in commit 64074bc ("Update version numbers for Zfh/Zfinx") of
+            riscv-isa-manual.
+
         - const: zk
           description:
             The standard Zk Standard Scalar cryptography extension as ratified