firmware: arm_scmi: Replace the use of of_node_put() to __free(device_node)

Use __free for device_node values, and thus drop calls to of_node_put.

The goal is simplify of_node reference cleanup by using this scope-based
of_node_put() cleanup to simplify function exit handling. When using __free
a resource is allocated within a block, it is automatically freed at the
end of the block.

This cleanup aligns well with the recent change in shmem.c to use __free
instead of explicit of_node_put() calls.

Message-Id: <20240827143838.1465913-3-sudeep.holla@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/firmware/arm_scmi/transports/mailbox.c

@@ -129,18 +129,16 @@ static int mailbox_chan_validate(struct device *cdev, int *a2p_rx_chan,
 
 	/* Bail out if provided shmem descriptors do not refer distinct areas  */
 	if (num_sh > 1) {
-		struct device_node *np_tx, *np_rx;
+		struct device_node *np_tx __free(device_node) =
+					of_parse_phandle(np, "shmem", 0);
+		struct device_node *np_rx __free(device_node) =
+					of_parse_phandle(np, "shmem", 1);
 
-		np_tx = of_parse_phandle(np, "shmem", 0);
-		np_rx = of_parse_phandle(np, "shmem", 1);
 		if (!np_tx || !np_rx || np_tx == np_rx) {
 			dev_warn(cdev, "Invalid shmem descriptor for '%s'\n",
 				 of_node_full_name(np));
 			ret = -EINVAL;
 		}
-
-		of_node_put(np_tx);
-		of_node_put(np_rx);
 	}
 
 	/* Calculate channels IDs to use depending on mboxes/shmem layout */

drivers/firmware/arm_scmi/transports/smc.c

@@ -84,12 +84,11 @@ static irqreturn_t smc_msg_done_isr(int irq, void *data)
 
 static bool smc_chan_available(struct device_node *of_node, int idx)
 {
-	struct device_node *np = of_parse_phandle(of_node, "shmem", 0);
-
+	struct device_node *np __free(device_node) =
+					of_parse_phandle(of_node, "shmem", 0);
 	if (!np)
 		return false;
 
-	of_node_put(np);
 	return true;
 }