doc: document buffer.from returns internal pool buffer

Fixes: #22139

Co-authored-by: Mritunjay Goutam <[email protected]>

PR-URL: #32703
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Rich Trott <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: James M Snell <[email protected]>

doc/api/buffer.md

@@ -379,9 +379,10 @@ A `TypeError` will be thrown if `size` is not a number.
 
 The `Buffer` module pre-allocates an internal `Buffer` instance of
 size [`Buffer.poolSize`][] that is used as a pool for the fast allocation of new
-`Buffer` instances created using [`Buffer.allocUnsafe()`][] and the deprecated
-`new Buffer(size)` constructor only when `size` is less than or equal to
-`Buffer.poolSize >> 1` (floor of [`Buffer.poolSize`][] divided by two).
+`Buffer` instances created using [`Buffer.allocUnsafe()`][],
+[`Buffer.from(array)`][], and the deprecated `new Buffer(size)` constructor only
+when `size` is less than or equal to `Buffer.poolSize >> 1` (floor of
+[`Buffer.poolSize`][] divided by two).
 
 Use of this pre-allocated internal memory pool is a key difference between
 calling `Buffer.alloc(size, fill)` vs. `Buffer.allocUnsafe(size).fill(fill)`.
@@ -571,6 +572,9 @@ const buf = Buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);
 A `TypeError` will be thrown if `array` is not an `Array` or other type
 appropriate for `Buffer.from()` variants.
 
+`Buffer.from(array)` and [`Buffer.from(string)`][] may also use the internal
+`Buffer` pool like [`Buffer.allocUnsafe()`][] does.
+
 ### Class Method: `Buffer.from(arrayBuffer[, byteOffset[, length]])`
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 added: v5.10.0
@@ -2733,10 +2737,11 @@ to one of these new APIs.*
   uninitialized, the allocated segment of memory might contain old data that is
   potentially sensitive.
 
-`Buffer` instances returned by [`Buffer.allocUnsafe()`][] *may* be allocated off
-a shared internal memory pool if `size` is less than or equal to half
-[`Buffer.poolSize`][]. Instances returned by [`Buffer.allocUnsafeSlow()`][]
-*never* use the shared internal memory pool.
+`Buffer` instances returned by [`Buffer.allocUnsafe()`][] and
+[`Buffer.from(array)`][] *may* be allocated off a shared internal memory pool
+if `size` is less than or equal to half [`Buffer.poolSize`][]. Instances
+returned by [`Buffer.allocUnsafeSlow()`][] *never* use the shared internal
+memory pool.
 
 ### The `--zero-fill-buffers` command line option
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